In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people.

The underground cities of the Byzantine Empire

This TED-Ed video explores the mysterious cave cities of Cappadocia. Although their oldest sections may go back to the Bronze Age, most of these subterranean complexes were excavated during the Byzantine period, when the locals went underground to take shelter from Arab raiders. Monasteries were also cut into pinnacles of the local tufa, and decorated with frescoes that have often survived to the present.

Why are ancient ruins underground?

When cities fall into disrepair, it's often easier to flatten what you can and build on top. This is why modern archaeologists frequently discover ruins underground, revealing generational layers of cities rebuilt over time. This video explores major examples of this principle, from ancient Troy to even modern Seattle.

The aqueducts and cisterns of Constantinople

The system of aqueducts that supplied Byzantine Constantinople with water had more than 500 kilometers of channels. These channels fed hundreds of cisterns. The largest were open pools (one, now drained, houses an entire modern shopping center); but the most impressive were vast covered chambers like the Basilica Cistern, still a highlight of any visit to Istanbul.

Enter the Mayan underworld through this 3-mile cave

Discoveries in Belize's Actun Tunichil Muknal (ATM) cave suggest the cave was once a significant site for sacred Mayan ceremonies in antiquity. New research reveals how the Mayans conducted rituals to re-enact a specific creation myth, often staged in desperate times and aimed to invoke the gods for a "rebirth" amid drought and turmoil. Read more on the enigmatic research here.

Visualizing Byzantium in the year 1200

This is a computer reconstruction of the Byzantine capital at its apogee, just before the Fourth Crusade. Alongside detailed renderings of the Hippodrome and Hagia Sophia, it includes dozens of the imperial city’s less famous monuments, many of which can still be found in modern Istanbul. The reconstruction is a work in progress, and the Byzantium 1200 X account routinely posts updates.

A history of China's ancient hidden tombs

Like many ancient cultures, the Chinese had a tradition of burying the dead in elaborate tombs, which would serve as both burial places and residences for the deceased. Archaeological evidence of these tombs, including those of former emperors, provides insights into the country's cultural evolution.

The impressive walls of Constantinople

This video explores the land walls of Constantinople, built on the orders of Theodosius II in the mid-fifth century. They consisted of a triple line of defenses, studded with hundreds of towers and supplemented with a moat. The walls were besieged dozens of times, but were only broken in 1453 by the power of Ottoman cannons. As repaired by the Ottomans, the walls are still largely intact today.

Go inside Queen Meresankh III's tomb

Examine art, explore the structure, and let yourself be transported back 3,000 years to when the granddaughter of the Pharaoh Khufu was buried. The site, first discovered in 1927, is known as a unique underground chapel with preserved depictions of the daily life of ancient Egyptian royals, and features one of the earliest known canopic jars, vessels used to store the organs of mummified individuals.

The Chora Church, the height of Byzantine art

The Palaeologan Renaissance took place in the final centuries of Byzantium, and in the face of steep political and economic decline. Perhaps the movement’s most famous artistic product is the Chora Church in Istanbul. Renovated in the early fourteenth century by Theodore Metochites, a learned court official, the church features remarkably vibrant mosaics and frescoes. Although the building was recently reconverted into a mosque, most of its decorations are still visible.

Pompeii's buried secrets are still being revealed

Despite digging for decades, archaeologists are still uncovering new insights into life before the blast that buried Pompeii. Follow a journalist's footsteps as they explore the ruins of Pompeii in this article. The ruins were discovered in the 1700s, and formal excavations throughout the 19th and 20th centuries revealed temples, mansions, and entire streets, while a third of the city remains to be excavated.

Why Turkey's earthquakes were so deadly

The death toll from February 2023 has reached the tens of thousands, making it one of the deadliest natural disasters of the century. The intense seismic activity combined with poor and unregulated construction in many areas to drive fatalities....

Toronto's downtown has 18 miles of underground pedestrian tunnels

Known as the "Path," these tunnels have helped reduce pedestrian traffic on Toronto's busy downtown streets for over a century. They were first built by local business owners, prompting a network effect of add-on tunnels.

NYC's first subway was built largely in secret

In 1870, Alfred Ely Beach secretly tunneled under Broadway in 58 nights, disguising his pneumatic subway as a mail tube to fool Tammany Hall, the corrupt political machine that ran New York City. Nearly half a million New Yorkers rode it before politics, and a stock market crash killed the project.

Human settlements may be older than previously thought

This narrative article follows an archaeological team as they sift through the remains of Nahal Ein Gev II, an ancient village near the Sea of Galilee in Israel. Abandoned about 12,000 years ago, the site has been investigated for years and...

How the underground maze below the Gaza Strip works

Hamas militants have constructed a web underneath the Gaza Strip filled with tunnels, residential areas, bunkers, and more. This article and illustrations explore the underground maze as detailed in photo and video evidence and witness accounts.

Machu Picchu, 101

Machu Picchu was built right on top of two intersecting fault lines, which makes it even more baffling how its temples and terraces have survived for more than 500 years—especially since no mortar was used to hold the precisely cut stones together. As this three-minute NatGeo video explains, this ingenious construction method allows the stones to bounce in place when earthquakes hit, shaking and rattling but rarely collapsing.

The massive sinkholes of China

Parts of China's limestone-rich terrain is fertile ground for massive caves, where some of the world's largest sinkholes are located. Hidden away in dense, lush forests, geologists are frequently discovering new sinkholes to explore. This piece...

While constructing the tunnel connecting the UK and France, satellite positioning systems were supplemented by paleontologists on either side of the tunnel, who analyzed fossils to ensure excavation was at the correct depth.

The ancient engineers inspiring modern building practices

Modern concrete structures need replacing every 50 to 100 years, so why are buildings by the Maya, ancient Rome, and ancient China still standing strong? This article details how scientists are looking into humanity's past for clues on how to craft long-lasting structures. Part of the problem is adopting old material recipes to hold up to modern demands.

Inside the most crowded place on Earth

Once the densest place on Earth, Kowloon Walled City was a chaotic labyrinth of stacked homes, hidden corridors, and thriving underground life.

As of 2025, humans have only dug 0.2% the way to Earth's center

The Kola Superdeep Borehole revealed two billion-year-old fossils and underground water, but the immense temperature and pressure prevented further tunneling. Beyond those depths, scientists know of Earth's interior by analyzing how seismic waves move.

See ten of the most amazing Mayan ruins

Hidden beneath the jungles of Mexico’s Yucatán Peninsula, Maya temples, pyramids, and cities reveal the civilization’s vast construction ambitions. Decades of archaeology have uncovered these sites, which are explored in detail in this guided video tour of 10 significant ruins.

Ceren: The Maya Pompeii (sans all the bodies)

The Maya village of Ceren in El Salvador was preserved by volcanic ash from 1,400 years ago, revealing insights into ancient Maya commoners' lives. Ceren villagers had autonomy in their daily activities, and excavations reveal evidence of communal decision-making and event hints at the presence of a community sauna. Dive into more of the archaeological finds on how businesses were run, how they prepared for disaster, and more.

The land where Greece's ancient language survives

In a remote corner of Turkey, locals speak Romeyka, a language with no written form and an "impressive" similarity to ancient Greek. This article details how the language may have survived and highlights the roughly 5,000 Romeyka speakers in the area. Research shows that Romeyka bears a startling resemblance to the Koine Greek spoken at the height of ancient Greek influence between fourth century BCE and fourth century CE.

The Maya built their cities with advanced engineering

Maya cities featured pyramids, palaces, causeways, ball courts, and water-management systems that were engineered to support large populations—often tens of thousands—without the use of metal tools, draft animals, or wheeled transport.

How the Turkish earthquake created a 100-mile rupture

A February 2023 earthquake devastated parts of Turkey and Syria destroying entire blocks, with more than 50,000 people killed. A scientific analysis revealed a fault line with a 100-mile-long rupture, where separate tectonic plates moved more than...

Machu Picchu is an ancient Incan citadel set high in the Andes Mountains in Peru, abandoned for centuries before its rediscovery in 1911.

Essential pipes, sewers, and cables lie buried beneath New York City

The Department of Design and Construction offers a tour of its work sites, explaining the complex systems that exist underground. Gas, electrical, telecom pipes, and many others, sprawl out underneath the entire city, with dozens of maps that help workers know where they're placed. This layout is unusual compared to the rest of the country, where wires are often present and visible above ground.

Eleven aqueducts funneled water to Rome's 1 million inhabitants

The Roman Empire's capital city was home to about one million people at its peak and managed to provide running water to many of its homes, fountains, and public baths. This was made possible by the 11 aesthetically grand aqueducts that poured into ancient Rome from the countryside.

What it's like to go inside the Great Pyramid of Giza

Tourists can actually enter the ancient wonder, taking a 15-minute jaunt through tight spaces some describe as uncomfortable. The focal point of the journey is the chamber of the dead pharaoh, historically significant but not always visually compelling. The author describes it as a cool bucket list item but wouldn't repeat it.

Why did this prehistoric culture regularly burn their homes?

This article explores why the Cucuteni-Trypillia culture may have regularly burned their homes. The Cucuteni-Trypillia culture is the oldest known in Europe, dating back to about 5,500 BCE in present-day Romania, Russia, and Ukraine. The...

The first coffeehouse opened in Constantinople

Coffeehouses began opening in modern-day Istanbul sometime in the 1500s. These cafes quickly became invaluable spaces for gathering and exchanging news and ideas.

Teotihuacán was already ancient when the Aztecs encountered it

By the time the Mexica reached Teotihuacán, the vast city had been abandoned for centuries. First settled around 400 BCE, the inhabitants developed monumental temples, canals, and a carefully planned urban grid centered on the Avenue of the Dead.

Boston opened the first subway tunnel in the US in 1897

By the end of the 19th century, nearly 400,000 people were packed into less than a square mile of downtown Boston, with 8,000 horses pulling trolleys through streets choked with noise, manure, and congestion. This prompted the city to pursue a then-controversial subway system.

Stonehenge has produced wild origin stories

Built before the wheel was invented, Stonehenge inspired increasingly fantastical explanations—from a 12th-century tale of Merlin and Nephilim giants to 1960s claims that aliens built it alongside the pyramids.

The unsolved mysteries of Machu Picchu

Who lived there? How did they get all that granite up there? Who were the 100 bodies found buried here, and why did some of them have elongated heads? Explore eight of Machu Picchu’s unanswered questions while scrolling through panoramic, clickable street-view images of the site, in this guide from Google Arts and Culture.

The high-tech mechanisms of the Roman Colosseum

The Roman Colosseum is one of the most iconic amphitheaters in the world and still partially stands today. Aside from its sheer size, the arena was equipped with some of the most high-tech engineering from the classical world, including sophisticated lifts, a huge retractable awning, and an underground network of tunnels, elevators, and trapdoors.

Explore the Mayan temple at Copan

Copan is a Mayan temple located in western Honduras, where Mayans dwelled for roughly 2,000 years. The acropolis there was abandoned in the tenth century but rediscovered in the 19th, and excavations of its many structures and tunnels continue to reveal more about Mayan history. Click through to tour its major temple and tunnels in this informative, impressive interactive.

Hagia Sophia, Istanbul's most famous and controversial landmark

A short video about the iconic Byzantine church. Still Istanbul’s most famous and, since its reconversion to a mosque, most controversial building. The recognizable dome has partially collapsed several times over the centuries, but remains a marvel of engineering. The mosaics, though fragmentary, are among the finest ever created and trace both the gradual evolution and the remarkable continuity of Byzantine art.

The Dokos shipwreck, the oldest discovered to date, is more than 4,000 years old

Many of the oldest shipwrecks yet discovered sank during the late Bronze Age as Mediterranean trade networks began to flourish. This video explores the nine oldest wreckage sites, topped by the wreck off the Greek island of Dokos.

In 2017, a hidden chamber was found in the Great Pyramid of Giza by measuring particles created in the collisions between cosmic rays and atmospheric particles.

Scientists are still confused how Machu Picchu was built

Machu Picchu, the 15th-century Inca city high in the Andes, continues to fascinate experts with its mysteries. The methods used to transport and carve its massive stones—some weighing 15 tons—remain unclear. Theories range from hundreds of men dragging the stones to innovative techniques like using expanding wet wooden wedges for precision carving.

The wild, early history of the tunnel across the English Channel

Britain and France today are connected by the Chunnel—a tunnel bored roughly 120 feet under the seabed of the notoriously choppy English Channel, which opened in 1994. The dream of integrating Britain with the rest of the continent this way began much earlier, with daring, physically impossible plans proposed as early as the 19th century. Check out the earliest plans here.

When Mount Vesuvius erupted in 79 CE, it buried the Roman city of Pompeii under 20 feet of ash, which preserved it for nearly 1,700 years.

Why are subway walls tiled?

In the early days of subway tunnels, architects needed to deal with dirt and moisture and make the cavernous stations less dank and dark. Ceramic tiles were easy to clean, and their glossy, bright finish helped illuminate the cave-like areas.

The three theories explaining how the pyramids were built

There's no consensus over how the ancient monuments were built, and no blueprints left behind. But centuries of study have produced three competing theories: a simple, massive external ramp, a more complex internal ramp, or a highly sophisticated water elevator.

History finds of 2021

The year’s most exciting discoveries include a Viking “piggy bank,” a lost Native American settlement and a secret passageway hidden behind a bookshelf

Tour the ancient world via beer

What did the people of yesterday make of beer, and how exactly did they make it? Explore the timeless beverage in this guide to ancient beers from around the world. Archaeological evidence suggests the rise of beer brewing may have coincided with humanity's shift from hunters to farmers. According to this article, beer was first enjoyed in ancient Mesopotamia, where paintings, poems, and myths glorified the porridge-like brew.

The archaeological sites uncovered through London's Crossrail Project

The Crossrail Project is an underground train system in London, which saw 26 miles of new tunnels created over more than a decade. The project provided unique access to long-buried layers of London's history, and a massive parallel archaeological excavation took place.

A nearby town proved even more archaeologically important than Pompeii

Herculaneum, buried under five times more ash than Pompeii, was sealed so completely that food, furniture, and entire buildings survived. This BBC documentary reveals how its discoveries have transformed scholars' understanding of the diets, work, and social mobility of ordinary Romans.