From ancient cisterns and water systems to mysterious caves, underground crypts, subterranean temples and even entire cities built beneath the earth, what our ancient ancestors have achieved is both mind-boggling and breathtaking. Here we feature ten incredible ancient subterranean structures whose construction is awesome.

The Amazing Subterranean Structure of the Basilica Cistern
Hidden beneath the city of Istanbul, Turkey, are hundreds of ancient cisterns that stored and supplied water to its inhabitants in the ancient past. The largest of these is the Basilica Cistern. So spectacular is the cistern that one could easily mistake it for a sacred subterranean temple. The Cistern is located just 150m (492.12 ft) southwest of the famous Hagia Sophia, and was built by the Byzantine emperor, Justinian I, in AD 532. It is 138 m (452.75ft) in length and 64.6 m (211.94ft) in width, covering an area of almost 1,000 square meters (92.90 sq m). This cistern is capable of holding up to 80,000 cubic meters of water.

Basilica Cistern in Istanbul Turkey. (Dpnuevo/CC BY-SA 3.0)

An incredible work effort went into its construction, with 336 marble columns supporting the structure. It is said that the majority of these columns were recycled from older buildings (a process known as ‘spoliation’), possibly brought to what was then Constantinople from the various parts of the Byzantine Empire, as well as those used for the construction of the Hagia Sophia. Perhaps the most iconic example of spoliation is the re-use of the heads of Medusa as the bases of two columns located in the northwest corner of the cistern. According to tradition, the heads were oriented sideways and inverted to counter the power of Medusa’s deadly gaze.

The Mysterious Shell Grotto of Margate
Thirty-five miles north of Dover is the English town of Margate in Kent – a coastal town with 57,000 inhabitants and a proud maritime history.

The mysterious shell grotto of Margate. (Keith Edkins/CC BY-SA 2.0 Deed)

What makes Margate special is the presence of a mysterious grotto, which has come to be known as the ‘Shell Grotto of Margate’. In 1835, the local school principal, James Newlove, wanted to build a duck pond in his garden. While digging, his shovel disappeared into an opening underneath a displaced capstone. He lowered his son Joshua on a rope to retrieve the item. Upon returning the boy spoke of tunnels full of shell decorations. Excavations revealed a spectacular grotto covered by more than 4.6 million seashells, spread in a mosaic over 600 m2.

Since the discovery in 1835, people have speculated about the true meaning of this place. What makes the shell grotto of Margate so mysterious is that there is nothing known about it. We do not know when the grotto was built, by whom and for what purpose.

Derinkuyu And the Underground Cities of Cappadocia
The region of Cappadocia in central Turkey is home to one of the most spectacular landscapes in the world, deep valleys and soaring rock formations dotted with homes, chapels, tombs, temples and entire subterranean cities harmoniously carved into the natural landforms.

One hundred square miles with more than 200 underground villages and tunnel towns complete with hidden passages, secret rooms and ancient temples and a remarkably storied history of each new civilization building on the work of the last, make Cappadocia one of the world’s most striking and largest cave-dwelling regions of the world.

A visual depiction of Derinkuyu. (Yasir999/CC BY-SA 4.0)

But nowhere else is the ingeniousness of the ancient architecture more visible than in the nearby subterranean city of Derinkuyu. Derinkuyu is eleven levels deep, has 600 entrances, many miles of tunnels connecting it to other underground cities, and can accommodate thousands of people. It is truly an underground city, with areas for sleeping, stables for livestock, wells, water tanks, and pits for cooking, ventilation shafts, communal rooms, bathrooms, and tombs. And Derinkuyu is not alone. More than forty complete underground cities have been discovered in the Cappadocia, many of them connecting to each other via tunnel.

Qanat Firaun, the Most Spectacular Underground Aqueduct of the Ancient World
The Qanat Firaun, otherwise known as the Gadara Aqueduct, is an ancient aqueduct that was built to supply water to the Roman-Hellenistic Decapolis, which now lie in present-day Syria and Jordan.  Although the Arabic name ‘Qanat Firaun’ means ‘Canal of the Pharaohs’, the massive canal, which demonstrates incredible engineering abilities, was not Egyptian but Imperial Roman, most likely influenced by the Persians.

Flooded tunnel section of the Qanat Firaun. (Pafnutius/CC BY-SA 3.0)

The 170-kilometre (105.63 mi) pipeline is not only the world’s longest underground aqueduct of the antiquity, it is also the most complex, and represents a colossal work of hydro-engineering.   The construction of the aqueduct demonstrates remarkable precision. The gradient of the tunnel was found to be 0.3 per thousand, meaning that it dropped only 30 cm (11.81 in) per kilometer (mi) – an amazingly shallow angle of decent. Along the main road of Gadara, archaeologists found basal pressure piles which suggested a siphon structure in order to supply the western outskirts of the city with fresh water, supposedly from sources 100 km (62.13 mi) away. By the time work ceased on the aqueduct, workers had excavated over 600,000 cubic meters (35.31 cubic ft) of limestone, comparable to more than a full quarter of the Great Pyramid’s total volume.

The Cult Centre And Underground World of Chavín de Huántar
Chavín de Huántar is an archaeological site located in the Ancash region of Peru, 250 km (155.34 mi)   north of the country’s capital, Lima. It is located at over 3000 m (9842.52 ft) above the sea level and is sandwiched between the desert coast to its west and the tropical Amazonian lowlands to its east. While carbon dating suggests that the site was occupied at least since 3000 B.C., it was around 1500 B.C. that Chavín developed into a sacred site. Chavín became a ceremonial and pilgrimage center for the religious world of the Andes.

One of the most interesting aspects of this site is its subterranean chambers. It is the carvings and the sculptures of these chambers that are its most impressive features. For instance, there is the Lanzon, a prism-shaped block of carved granite that is 4.5m (14.76 ft) in height. This block of granite begins with a broad feline head, and tapers down to a point stuck into the ground. This feline motif can also be seen in the carvings along the outer stone walls of the Castillo sector (the southern wing of the temple).

Detail of the Lanzon of Chauvin. (Dtarazona/CC BY-SA 3.0)

These carvings depict gargoyles (known as Cabeza Clavos), which are supposed to be the temple’s guardians. Apart from feline features, the gargoyles are said to have bird-like characteristics as well.  This iconography may help us to gain a better understanding of the cult that was practiced at Chavín.

The Incredible Sound Effects of Malta’s Hypogeum Hal Saflieni
The Hypogeum of Hal Saflieni in Malta is a UNESCO World Heritage Site which is believed to be the oldest prehistoric underground temple in the world.  The subterranean structure is shrouded in mystery, from the discovery of elongated skulls to stories of paranormal phenomena. But the characteristic that has been attracting experts from around the globe is the unique acoustic properties found within the underground chambers of the Hypogeum. Although not known for certain, it is believed that the hypogeum was originally used as a sanctuary, possibly for an oracle.

Photograph of the Hypogeum of Ħal-Saflieni made before 1910. (Public Domain)

It is for this reason that a unique chamber carved out of solid limestone and demonstrating incredible acoustic properties has been called ‘the Oracle Chamber’.  According to William Arthur Griffiths, who wrote ‘Malta and its Recently Discovered Prehistoric Temples’, a word spoken in the Oracle room is “magnified a hundredfold and is audible throughout the entire structure.  The effect upon the credulous can be imagined when the oracle spoke and the words came thundering forth through the dark and mysterious place with terrifying impressiveness.”

Rome’s Labyrinth of Subterranean Tunnels
As tourists wander the streets of Rome and flock to the incredible sites of the Colosseum and Roman Forum, few of them realize that beneath their feet lies something even more ancient – a maze of subterranean tunnels and quarries that date back to the very beginning of this ancient city.  The tunnels first began as quarries as the ancient Romans mined rock to build their city, which later expanded over the tunnels. Then, once the quarrying ended, people began using the underground labyrinth as catacombs, for mushroom farming and as an unofficial sewer system.

A view of the maze of subterranean structures under the city of Rome. (edk7/flickr)

During World War II, people used the tunnels as bomb shelters.  “Hundreds of kilometers of catacombs run underneath the town and its outskirts,” says Adriano Morabito, president of the association Roma Sotterranea (Underground Rome). “Some of the networks are well known and open to visitors, while others are still scarcely explored. Probably there are a number of lost catacombs, too.”

The Underground Caves of Nottingham
Below the streets of Nottingham, England, nearly 500 man-made caves are cut into the natural sandstone. Over the centuries, they have been used for a vast array of purposes, including dungeons, beer cellars, cess-pits, tanneries, malt-kilns, houses, wine cellars, tunnels, summer-houses, air-raid shelters, sand mines, and jails – most famously the one said to have held Robin Hood.

The earliest written record of Nottingham’s caves comes from a Welsh monk called Asser who when writing about Nottingham in 868 referred to the town as Tig Guocobauc, meaning house or place of caves in British.

(Enchufla Con Clave/CC BY-SA 4.0)

In 1067, the Normans arrived in the region and built a castle on an outcrop of sandstone. The Norman’s built their own town around the castle with streets radiating out from it towards what is now the market square in modern day Nottingham.  The exposed cliff of the sandstone outcrop made this an obvious place for the early citizens of Nottingham to make their home.  Records from visitors to Nottingham during the 1600s suggest that the occupants of these cave houses were generally poor and the caves were known as pauper holes.

Throughout the medieval period Nottingham continued to grow and prosper becoming a center for trades such as wool manufacture, tanning, alabaster carving and pottery production.  A number of these activities were undertaken in Nottingham’s caves. From the 1800s new caves were cut and existing ones extended as Nottingham’s industries and their need for storage space grew.  Unfortunately, redevelopment of Nottingham’s city center from the late 19th century onwards has meant that many of Nottingham’s caves have been lost.

The Longyou Caves
Located near the village of Shiyan Beicun in Zhejiang province, China, lies the Longyou caves – an extensive, magnificent and rare ancient underground world considered in China as ‘the ninth wonder of the ancient world’.  The Longyou grottoes, which are thought to date back at least 2,000 years, represent one of the largest underground excavations of ancient times and are an enduring mystery that have perplexed experts from every discipline that has examined them.  Scientists from around the world in the fields of archaeology, architecture, engineering, and geology have absolutely no idea how they were built, by whom, and why.

The Longyou grottoes date back 2,000 years. (Zhangzhugang /CC BY-SA 4.0)

First discovered in 1992 by a local villager, 36 grottoes have now been discovered covering a massive 30,000 square meters (322,917 sq ft) Carved into solid siltstone, each grotto descends around 30 meters (98.42 ft) underground and contains stone rooms, bridges, gutters and pools. There are pillars evenly distributed throughout the caves which are supporting the ceiling, and the walls, ceiling and stone columns are uniformly decorated with chisel marks in a series of parallel lines. Only one of the caves has been opened for tourism, chosen because of the stone carvings found inside which depict a horse, fish and bird.  The Longyou caves truly are an enigma that are still unexplained despite more than two decades of research.

The Ancient Catacombs Of Malta
The Paleochristian heritage of the Maltese Islands rates as the fourth most important cluster of such monuments in the Mediterranean Region following those of the Italy, Israel and of the Maghreb, of which its most prominent feature is its extensive concentration of subterranean burial grounds. The catacombs of Malta have been described by UNESCO as “excellent documents of the changing cultural, artistic and social climates of the Mediterranean world in the centuries going from the 3rd to the Centuries AD”.

In a period covering the mid-third to the early seventh century AD, burial grounds developed in Malta from a tradition of simple rock-cut tombs of the Phoenician and Hellenistic eras (700 BC – 100 AD). One remarkable feature of the Maltese catacombs is the co-mingling of religious rites, which includes clear references to Christianity, pagan practices and Judaism, all within the same locality.  This reflects the co-habitation of these different cultures within Late Roman society.  According to UNESCO, “this mixed feature of the Maltese catacombs is rarely equaled anywhere else in the Mediterranean.”