The Great Underground Constructions of the Ancient World

Hundreds, even thousands of years ago, when there was no modern equipment, people built spectacular underground structures.

Basilica Cistern

Marble columns in the Basilica Cistern in Istanbul. (Photo: Xinhua).

Hidden beneath the city of Istanbul, Türkiye, are hundreds of ancient cisterns that once stored and supplied water to its ancient inhabitants. The largest of these is the Basilica Cistern, so massive that it has been nicknamed the "Sunken Palace." The Basilica Cistern was built in 532 by the Eastern Roman emperor Justinian I to solve the city's drought problem. The crypt is 138 meters long, 64.6 meters wide, covers an area of ​​nearly 10,000 square meters and can hold up to 80,000 cubic meters of water.

The construction of the Basilica Cistern was a feat of engineering, with 336 marble columns supporting the vault. According to some experts, most of the columns were recycled from older structures. The crypt fell into disuse after the 10th century because maintenance was too costly and labor-intensive. Over the years, tons of mud covered the crypt until it was rediscovered and reinforced several times, starting in the 18th century.

Gadara Aqueduct

The underground Gadara aqueduct. (Photo: Ancient Origins).

The Gadara Aqueduct was built to supply water to a cluster of 10 Hellenistic-Roman cities in what is now Syria and Jordan. This engineering marvel belonged to the Roman Empire and was likely influenced by the Persians.

The 170-km canal system is not only the longest ancient underground water channel in the world, but also the most complex. The structure was built with great precision. The slope of the underground channel is extremely small, decreasing only 30 cm per km. The Gadara Canal carries fresh water from sources 100 km away to the western outskirts of the city. When the construction of the aqueduct was completed, workers had excavated more than 600,000 m3 of limestone, equivalent to more than a quarter of the total volume of the Great Pyramid of Giza.

Derinkuyu Underground City

Tunnel leading to the underground city of Derinkuyu. (Photo: Travel Turkey).

Beneath the cobblestone streets of Derinkuyu lies a network of ancient tunnels and chambers that could have housed 20,000 people. Located more than 85 metres below ground and spanning 18 levels, it is the largest underground city ever discovered.

The structure was rediscovered in 1963 when a local man kept losing chickens. After noticing that the chickens had fallen through a crack in his house while he was renovating, the owner found a dark passageway leading to the complex. Hundreds of houses in the area also have hidden passageways leading to the underground city. Interspersed among the nooks and crannies of the complex are rooms that were once used as meeting places, barns, kitchens, storage rooms, and small prisons. The structure even has an efficient ventilation system that allows fresh air to circulate deep within the labyrinthine structure.

The Derinkuyu Underground City served primarily as a refuge during war or times of hardship. The city's age remains controversial among scholars, but some estimates place it as far back as 2,800 years.

Margate Shell Caves

Margate Shell Caves in England. (Photo: Keith Edkins).

What makes the seaside town of Margate in Kent, England, special is the presence of the Margate Shell Grotto. In 1835, the local schoolmaster, James Newlove, wanted to build a pond in his garden. While digging, his shovel fell into a large crack under a boulder. He used a rope to lower his son down to retrieve the object. However, when he returned, the boy told of tunnels decorated with shells underneath.

Subsequent excavations revealed a spectacular cave containing more than 4.6 million sea shells embedded in a 600-square-meter mosaic. What makes the Margate Shell Cave so mysterious is that experts have no idea what it was made of. They don't know exactly when it was built, by whom, or for what purpose.

Rome's tunnel network

Part of the tunnel network beneath Rome. (Photo: Ancient Origins).

Beneath the streets of Rome, Italy, is a network of tunnels and quarries that date back to the city's earliest days. These tunnels were originally used by the ancient Romans to quarry stone for the city's construction. The city expanded and was built over the tunnels. Later, when the quarrying ended, the ancients began using the underground network as catacombs, mushroom farms, and as a drainage system. During World War II, they were also used as bomb shelters.

"There are hundreds of kilometres of tunnels running beneath the city and its suburbs. Parts of the network are well understood and open to visitors, while others remain poorly explored. There are probably many more lost catacombs ," said Adriano Morabito, president of the Roma Sotterranea association.