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.

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.

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.

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.

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.

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...

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....

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.

A West Berlin student dug a tunnel under the Berlin Wall—29 East Germans escaped

This podcast recounts how a young West Berlin student excavated a secret 135‑meter tunnel beneath the Berlin Wall in 1962. A total of 29 East Germans escaped to freedom, even as a Stasi mole threatened exposure.

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

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 a 3D reconstruction of Tenochtitlan, the Aztec capital that was home to an estimated population of 200,000 to 400,000.

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.

15,000 people from over 20 nations lived in these Lower East Side tenements

The Tenement Museum recreated authentic immigrant homes using artifacts from historic buildings that housed diverse communities between 1863 and 2011. Take a digital tour that explores the immigrant experience through carefully preserved living spaces and belongings.

In 1915, workers recovered a submarine-like vessel from the Chicago River, prompting fears of German espionage

Turkish delight recipes were initially kept secret

The chewy confection dates back to the 1700s, and initially was served at the sultan's court. The palace's secret recipes were eventually published in one of the earliest Ottoman cookbooks by Mehmet Kamil.

Decoding the Indus Valley script

About 100 years ago, archaeologists uncovered an ancient city along the bank of the Indus River in eastern Pakistan that dated back to 2,500 BCE, though its urban planning, grid-like roads, brick-lined streets, multi-story homes, and sanitation and...

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

The archaeological discovery that shifted scientists' understanding of human evolution

In 2003, archaeologists in Indonesia uncovered the remains of a 3-foot-tall skeleton that appeared to belong to a new type of human. Read this article to learn how the discovery of this 50,000-year-old skeleton upended the idea that human evolution...

A $7.5M renovation aimed to protect Fallingwater from climate-related damage

The exhaustive plan took over three years to reach the finish line. The majority of the expenses went toward hiring skilled laborers to address issues such as water damage in the unique location.

A German town transforms its entire city hall into a massive Advent calendar

Gengenbach turns its 18th-century town hall into a 24-window Advent calendar attracting up to 220,000 visitors each December. Each night reveals new art, reviving winter tourism in the town.

Meet a 90-year-old who built his own hobbit-inspired house

A retired carpenter built himself a kind-of Hobbit house, and is living comfortably off the grid at 90 years old, tourists notwithstanding. Learn how he did it with this video.

A basement of mechanical systems—collectively called the technosphere—supports B2

Twenty-six underground air handlers heat, cool, filter and manage the humidity of the air across the biomes of Biosphere 2. The above-ground Energy Center complex provides continuous power to these and other systems, including heating and cooling water for laboratory experiments and personal use.

Graffiti dates back to at least ancient Pompeii, where citizens scrawled messages to one another on public walls

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

Explore a gallery of O'Neill cylinder space settlements

The structures consist of a pair of cylinders with a total enclosed land area of 500 square miles and can house several million people. Each is approximately 20 miles long, 4 miles in diameter, and contains three mirrors that open and close to form a day-night cycle inside.

A map of Barcelona from 150 BCE to 2010

Watch Barcelona evolve from Iberian settlements in 150 BCE to Spain’s second-largest city in the modern day by toggling this chronological series of 27 maps. Accompanied by a short contextual blurb, each map shows Barcelona’s steady urbanization over more than two millennia. For those captivated by the interactive, read this interview with one of the project’s key cartographers. He discusses how the mega-map was created and what it reveals about Barcelona’s history.

See photos of Meteora, a mountainous site in central Greece, home to 14th-century monasteries perched atop soaring outcroppings.

The idea for the Federal Reserve was conceived in secret in 1910—with bankers donning duck hunt gear for disguise while traveling to a remote country club on Georgia's Jekyll Island

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Before the current East Wing ballroom project, only two White House renovations in the past 100 years cost more than $10M.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Explore the history, structure, and species of Australia's Great Barrier Reef with this interactive journey narrated by Sir David Attenborough.

See 33 images that became central to huge scandals, including a young Charles and Camilla, Michael Jackson's baby on a hotel balcony, and Hugh Grant's mugshot.

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

Explore a list of the 100 best novels of all time, compiled by some of the world's best living writers, including Salman Rushdie, Stephen King, and Jennifer Egan.

Search a massive database of over 4 decades of clues from the TV quiz show 'Jeopardy!'

Existentialist writer Jean-Paul Sartre coined the famous phrase 'Hell is—other people' in his play 'No Exit'

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.