The depiction of the Colossus guarding the port of Rhodes dates from centuries after the statue disappeared but eventually became the image we still have of this monumental figure of the god Helios. Credit: ÁTICO DE LOS LIBROS.

Colossal Sculptures That Vanished Without a Trace

Earthquakes, wars, and the passage of time itself have caused some of history’s most monumental sculptures to vanish. What remains of them are texts, archaeological remains, and—in more recent cases—images that allow us to reconstruct part of what was lost. From the Colossus of Rhodes to the Buddhas of Bamiyan, these traces provide insight into how they were erected and, in some cases, help us decide what to do with what remains.

MARÍA GÓMEZ BRAVO | Tungsteno

In March 2001, television viewers around the world watched the destruction of the Afghan Buddhas of Bamiyan. For weeks, explosions ordered by the Taliban regime gradually reduced the two ancient sculptures to rubble. Twenty-five years later, those images have become a symbol of the deliberate destruction of cultural heritage and continue to fuel the debate about what happens when monumental works—designed to last for centuries—disappear.

Long before Bamiyan, earthquakes, fires, wars, the passage of time, and the reuse of their materials caused some of the colossal monuments of antiquity to vanish. Of many of these magnificent sculptures, only traces remain: the texts that described them, the sites where they once stood, scattered fragments, or the imprints they left on the landscape. Today, these traces are complemented by new tools that allow us to reconstruct and study monuments that no longer exist physically.

 

A Colossus in Constant Reconstruction

 

Few sculptures have inspired as much literature while leaving us with so little certainty as the Colossus of Rhodes. The image of the giant towering over the entrance to the harbor is part of the collective imagination, although we do not know whether it actually stood there. This interpretation emerged centuries after the bronze statue disappeared and ultimately shaped the way we still imagine the colossal figure dedicated to the god Helios today.

Today we know that the Colossus was erected between 295 and 283 BC to commemorate Rhodes’ victory following the siege led by Demetrius Poliorcetes and that it stood approximately 34 meters tall. Nathan Badoud, author of The Colossus of Rhodes: Archeology of a Lost Wonder, suggests that it may have been located near the present-day Palace of the Grand Master. There is also broad consensus on the cause of its destruction: an earthquake toppled it barely half a century after its construction.

Beyond these facts, much remains uncertain. No identified fragments of the statue have survived, and ancient sources offer only sparse descriptions. Archaeologists and historians have reviewed the topography of ancient Rhodes, classical texts, and the political context in which it was erected to try to determine where it stood, what it looked like, and what it meant to a city that had by then become one of the great powers of the eastern Mediterranean.

 

Research drawing on classical literature, combined with disciplines such as topography and engineering, challenges the image and location traditionally associated with the Colossus. Photo: Culture Club/Getty Images.

 

Engineering also plays an important role in this research. Knowledge of Hellenistic metallurgy, materials, and the structural behavior of bronze makes it possible to assess the feasibility of the various hypotheses regarding its construction. Ancient sources, including the texts of Pliny the Elder, remain fundamental, but they are no longer the only tools available for attempting to reconstruct a colossus that disappeared more than two thousand years ago.

Reconstructing from the Original Site

 

We do not know for certain when or how the Statue of Zeus at Olympia disappeared. We do know that around 430 BC, a monumental figure of Zeus presided over the temple dedicated to him at the Greek sanctuary in the Peloponnese. The building had been erected a few decades earlier, in the first half of the 5th century BC, and its pediments and metopes were decorated with an extensive sculptural ensemble. Opposite the temple, outside the sacred precinct of the Altis, stood the workshop where Phidias worked—the sculptor responsible for the monumental depiction of Zeus.

Excavations at the site uncovered terracotta molds, ivory fragments, and materials used for glassworking. A small cup bearing the inscription Pheidiou eimi (“I belong to Phidias”) was also found. The chronology of the finds dates activity in the building to the third quarter of the 5th century BC, coinciding with the period when the sculpture—one of the Seven Wonders of the Ancient World—was constructed.

 

The materials used in Phidias’s great sculpture of Zeus and the methods used to make some of its components are known from molds found at his workshop,outside the sacred precinct of the Altis. Credit: Hulton Archive/Getty Images.

 

The Statue of Zeus was a chryselephantine sculpture of extraordinary dimensions. Art historian Judith M. Barringer estimates its height at around 13.5 meters, a scale that required the figure to be constructed using an internal framework—likely made of wood—over which various materials were applied, primarily ivory for the skin and gold for the garments. The molds found in the workshop allow us to study how some of these components were made, although we still do not know precisely how the entire figure was assembled.

The combination of materials also affected its preservation. Ivory and wood are sensitive to changes in humidity. When the Greek traveler and geographer Pausanias visited Olympia in the 2nd century CE, he noted the presence of olive oil in a depression in front of the statue. This has been interpreted as a possible measure to protect the ivory from environmental conditions, although later research also suggests an optical function: the surface may have helped reflect light onto the figure. Both interpretations remain possible.

 

The Images That Survived the Buddhas

 

After the explosions, the two large niches at Bamiyan were left virtually empty, and the remains of the sculptures lay scattered at their feet. To study them, researchers had access to something that never existed in the case of the Colossus of Rhodes or the Statue of Zeus at Olympia: photographs taken before their destruction.

 

The world’s tallest standing Buddha statue, located in the province of Bamiyan, was destroyed by explosions ordered by the Taliban regime in 2001. Credit: JEAN-CLAUDE CHAPON/AFP/GETTY.

 

Just three years later, Armin Grün, Fabio Remondino, and Li Zhang of ETH Zurich drew on three collections of images from before 2001 to digitally reconstruct the Great Buddha. The study, published in The Photogrammetric Record, combined photographs taken by visitors with others taken specifically for measurement purposes. Photogrammetry made it possible to reconstruct its shape and dimensions and generate a three-dimensional model.

Digital techniques were also applied to the cliff face. Laser scanning and photogrammetry were used to document the niches and remains and obtain an accurate record of their condition. Years later, some projects incorporated these data into virtual environments to study different conservation and restoration measures before undertaking any work on the site.

In 2017, a study published in PLOS ONE analyzed the layers of paint adhering to some fragments to reconstruct part of the history of their decoration. The analyses identified egg proteins used as a binder in the original layers and cow’s and goat’s milk in later repaintings, making it possible to distinguish between different stages and materials used on the Buddhas over time.

 

Reconstructing or Preserving the Absence

 

Digital technologies have made it possible to reconstruct the appearance of the Buddhas with a precision that was unthinkable a few decades ago. But turning those models into a physical reconstruction raises a different debate. Twenty-five years after their destruction, the future of the Bamiyan niches remains unresolved.

Proposals have ranged from leaving them empty to partially or fully reconstructing some of the figures. UNESCO and experts who have worked on the site have spent years analyzing the various possibilities. It is not merely a matter of determining what can be reconstructed: it is necessary to assess the stability of the cliff, the original fragments that could be reused, the authenticity of any potential intervention, and its significance for the communities connected to the valley.

 

The possible reconstruction of the Bamiyan Buddhas, destroyed by the Taliban regime in 2001, has kept alive the debate about how much of their absence should be preserved. Credit: KAMRAN SHAFAYEE/AFP via Getty Images.

 

Added to these questions is the historical value of the destruction itself. The 2001 explosions forever altered the site, and their traces are now part of Bamiyan’s recent history. For this reason, one proposal is to leave at least one of the niches empty as a testament to what happened, while others advocate restoring, to varying degrees, the presence of the Buddhas.


Tungsteno is a journalistic laboratory that explores the essence of innovation.

El auge del subsuelo: cómo las ciudades están ganando espacio bajo tierra

Cuando el espacio disponible en superficie empieza a agotarse, algunas ciudades buscan otras formas de crecer. Bajo calles y edificios se extiende una red cada vez más compleja de infraestructuras que, más allá de los servicios básicos y el transporte, empieza a asumir nuevas funciones dentro del desarrollo urbano.

MARÍA GÓMEZ BRAVO | Tungsteno

En la lucha por ganar espacio, las urbes fueron conquistando las alturas. Rascacielos y torres insignias definieron el horizonte y se convirtieron, muchas veces, en icono de las grandes capitales. Pero bajo tierra también se ha venido gestando una revolución que se inició desde una visión puramente funcional: hacer desaparecer bajo las calles las infraestructuras necesarias para que la ciudad funcionara. Primero fueron las alcantarillas y conducciones de agua. Después llegaron el ferrocarril, el metro, el cableado, los aparcamientos, los refugios y hasta las carreteras.

La falta de suelo en superficie ha vuelto cada vez más atractivo ese espacio que no se ve, donde cada nueva infraestructura debe encontrar su lugar entre las anteriores y evitar ocupar el que necesitarán las siguientes. Pero no es la única razón que explica lo que está ocurriendo bajo las ciudades. Hay que mirar más allá de la escasez de metros: desde la geología hasta el clima.

 

Una ciudad excavada en la roca

 

El suelo de granito sobre el que descansa buena parte de Helsinki es una de las razones que explican su desarrollo bajo tierra. Este lecho rocoso ha servido de molde para túneles, aparcamientos, instalaciones energéticas y espacios deportivos. La ciudad lleva aprovechando sistemáticamente sus condiciones desde los años sesenta. Cuando comenzó a elaborar su primer plan específico para el subsuelo, ya había excavado alrededor de nueve millones de metros cúbicos de roca, repartidos entre unas 400 instalaciones y túneles.

Algunas de esas infraestructuras tienen más de una vida. Las instalaciones subterráneas pueden funcionar como refugios de protección civil y los espacios recreativos incluyen piscinas y equipamientos deportivos excavados en la roca. Por las galerías de uso común discurren además tuberías de calefacción y refrigeración urbana, grandes cables eléctricos y redes de telecomunicaciones. Solo estas conducciones sumaban ya unos 300 kilómetros cuando se redactó el plan.

 

La piscina subterránea de Itäkeskus se encuentra a 50 metros bajo tierra, excavada en la roca, en uno de los refugios de protección civil de Helsinki transformados para uso cotidiano. Crédito: ALESSANDRO RAMPAZZO/AFP via Getty Images.

 

La creciente demanda de espacio llevó a la capital finlandesa a plantearse no sólo dónde construir las siguientes instalaciones, sino qué partes de la roca convenía no ocupar todavía. El resultado fue el Underground Master Plan, que ordenaba las principales cavidades, instalaciones y túneles, tanto existentes como futuros, y reservaba espacio para proyectos a largo plazo. El plan inicial identificó 40 nuevas áreas como reservas de roca y más de 100 emplazamientos para futuras construcciones. El ingeniero Ilkka Vähäaho, que dirigió durante años la división geotécnica de Helsinki, explica que el rápido crecimiento de la construcción subterránea desde comienzos de este siglo hizo cada vez más necesario controlar dónde se excavaba.

El documento con el que Helsinki presentó su primer plan lo resumía de una forma mucho más sencilla: excavar la roca es una acción que solo puede hacerse una vez. Un edificio puede sustituirse y una parcela cambiar de uso, pero las cavidades excavadas en la roca permanecen durante mucho más tiempo y pueden cerrar el paso a otras infraestructuras. Helsinki empezó a planificar también ese vacío.

 

Escudo para el invierno

 

El frío determina la manera de moverse y hasta de vivir en Montreal (Canadá). Bajo sus calles se teje una red de galerías que conecta edificios, oficinas, universidades, hoteles, centros comerciales y otros equipamientos sin necesidad de pisar la calle. Una especie de ciudad subterránea que utilizan cerca de 500.000 personas cada día y que permite atravesar buena parte del centro a cubierto.

Pero los cerca de 32 kilómetros de corredores que componen la red RÉSO no nacieron como respuesta a esas condiciones climáticas. Su desarrollo comenzó entre 1962 y 1967 alrededor de Place Ville Marie y fue creciendo ligado a las grandes operaciones inmobiliarias del centro y a la expansión del metro, especialmente durante los años previos a la Expo 67.

 

El centro comercial Montreal Trust forma parte de RÉSO, la red subterránea que conecta edificios, comercios, hoteles y estaciones de metro en el centro de Montreal a través de cerca de 32 kilómetros de corredores. Crédito: Pascal QUITTEMELLE/Gamma-Rapho via Getty Images.

 

Sin un gran proyecto que dibujara desde el principio, las conexiones fueron sumándose durante décadas a medida que nuevos edificios se incorporaban al sistema. Un crecimiento orgánico que convirtió esta red subterránea en una ventaja extraordinaria tanto para la economía como para la movilidad de sus habitantes durante las temporadas heladas. Décadas después, resulta difícil separar una cosa de la otra.

Porque el frío sí condiciona los desplazamientos de los usuarios en la ciudad. Un estudio de Luis F. Miranda-Moreno y Aleksiina Lahti encontró que los flujos peatonales disminuyen durante el invierno y que la temperatura, la humedad, el viento y las precipitaciones influyen en la actividad a pie. Sin embargo, esta tela de araña que interconecta el centro de la ciudad bajo tierra ha quedado tan ligada a la manera de entender la ciudad que a día de hoy, es difícil encontrar diferencias significativas en los recorridos que hacen sus habitantes en función del clima exterior.

El análisis realizado por el profesor John Zacharias comprobó que no producía diferencias significativas ni en la distancia caminada ni en la proporción del trayecto realizado bajo tierra. Pesaba mucho más la localización del punto de partida. Lo que había empezado como una suma de conexiones se ha incorporado a la forma cotidiana de atravesar el centro.

 

A 150 metros bajo Singapur

 

Frente a la costa de Singapur, cinco enormes cavernas se esconden a unos 150 metros bajo la isla de Jurong. Las Jurong Rock Caverns pueden almacenar hasta 1,47 millones de metros cúbicos de hidrocarburos para la industria energética y química de la isla. Excavarlas permitió liberar unas 60 hectáreas en superficie para otras actividades industriales. En un país de poco más de 730 kilómetros cuadrados, esa superficie adquiere otro valor.

Singapur lleva décadas librando una batalla por la conquista de espacio donde apenas lo hay. Ha ganado terreno al mar, ha construido en altura y también ha empezado a mirar hacia abajo. El ingeniero Yingxin Zhou lo explicaba con una imagen muy gráfica durante el World Urban Forum de 2018: "Singapur no tiene minas de oro, petróleo o diamantes; lo que extrae bajo tierra es espacio”.

 

Singapur acumula ya alrededor de 300 kilómetros de túneles y prevé construir otros 60 durante la próxima década, según el Master Plan 2025. Crédito: John Seaton Callahan.

 

Las Jurong Rock Caverns son quizá la expresión más espectacular de esa búsqueda, pero buena parte de esa transformación permanece oculta bajo el conjunto de Singapur. En los niveles más próximos a la superficie se sitúan los comercios, aparcamientos, servicios y conexiones peatonales, mientras que a mayor profundidad están las líneas ferroviarias, carreteras y redes de agua, saneamiento y electricidad. En total, Singapur acumula ya alrededor de 300 kilómetros de túneles y prevé construir otros 60 durante la próxima década, según el Master Plan 2025.

La creciente ocupación del subsuelo de Singapur ha obligado también a planificarlo a largo plazo. En 2007, el Gobierno creó un grupo de trabajo interinstitucional específico y, tres años después, su desarrollo se incorporó a la estrategia económica del país, como describen Zhou y Jian Zhao en un estudio publicado en Tunnelling and Underground Space Technology. El Master Plan 2025 explora ahora nuevos usos, desde cavernas para almacenamiento hasta galerías de servicios e infraestructuras energéticas, y reserva espacio para las que puedan llegar en el futuro.

Pero ganar superficie tiene también un coste bajo tierra. Los espacios subterráneos requieren iluminación, ventilación y, en muchos casos, deshumidificación. Un estudio publicado en Sustainable Cities and Society identificó también beneficios potenciales asociados al transporte, la ocupación compacta del suelo, las infraestructuras y la energía geotérmica. La profundidad, por sí sola, no determina la sostenibilidad: importa qué se traslada bajo tierra, qué espacio libera en la superficie y durante cuánto tiempo podrá aprovecharse.


Tungsteno es un laboratorio periodístico que explora la esencia de la innovación.

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Sacyr leads desalination proposal to strengthen regional water supply

  • The proposal explores a potential desalination facility in Baja California, Mexico, and a pipeline near the U.S. border as part of a broader effort to evaluate mutually beneficial regional water supply opportunities.

Sacyr has taken another step forward with the proposed Northern Gulf of California Desalination Plant, a desalination solution designed to strengthen region’s long-term water supply.

The Board of Directors of the Water Infrastructure Finance Authority of Arizona (WIFA) approved the initial stage of the appraisal study for the proposal, which is led by Sacyr and includes Arcadis, U.S., Inc. and Plenary Americas US Holdings Inc. as a participant.

The study will be evaluating the viability of a new desalination plant in Baja California, Mexico, and a pipeline to convey the desalinated water to Morelos Dam, on the U.S. border, where it would be integrated into the Colorado River system for distribution and use in Mexico. The water produced would be exchanged for part of Mexico’s Colorado River allocation, which could be made available to Arizona. 

Ultimately, it could increase Arizona’s supply by up to 500,000 acre-feet per year, equivalent to 1.7 million cubic meters per day, between 2034 and 2039.

A solution to water supply challenges 

Arizona faces water supply challenges, worsened by prolonged drought. This is putting pressure on traditional water sources, and has led the State to study long-term alternatives to diversify supply in the coming decades.

WIFA is an Arizona government agency that financially supports the development of solutions to ensure the state’s water future. Its evaluation process reviews proposals capable of providing new, reliable and sustainable water sources.

Under the proposal, Arcadis would serve as lead engineering firm, while Sacyr would lead construction, operations and maintenance. Sacyr would also work with Plenary Americas on the project’s financial development.

During this initial phase, Sacyr will advance early studies to define the project’s technical, financial, environmental, cultural and regulatory viability, reduce uncertainty and provide WIFA with information for future decisions within its phased evaluation process.

Approval of the scope authorizes only this first stage of analysis and does not represent a decision on delivery or on future funding requests, which WIFA will evaluate separately based on the results.

Even so, it places the Sacyr-led proposal in the next phase of the process to identify long-term water supply solutions for Arizona.

International experience in desalination and water management

Sacyr Water brings its international experience in the design, construction and operation of water infrastructure, particularly in desalination, treatment and reuse, to develop solutions to water stress and help ensure secure, efficient resources.

This step strengthens Sacyr’s presence in North America and its position in the water sector in a strategic market, in line with its commitment to sustainable, innovative and resilient infrastructure.

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