The Mir mine, also called the Mirny mine, is an open pit diamond mine located in Mirny, Sakha Republic, in the Siberian region of eastern Russia. The mine is >525 meters (1,722 ft) deep (4th in the world) and has a diameter of 1,200 m (3,900 ft), and is one of the largest excavated holes in the world.

The research and development carried out in Peenemünde was not only crucial to the course of WWII, but impacted the future of weapons of mass destruction, as well as space travel.

On the Maryland side of the Potomac River just west of Chesapeake Bay, the largest shipwreck fleet in the Western Hemisphere sits half-sunk and decomposing.

The Kinzua Bridge or the Kinzua Viaduct was a railroad trestle that spanned Kinzua Creek in McKean County in the U.S. state of Pennsylvania. The bridge was 301 feet (92 m) tall and 2,052 feet (625 m) long. Most of its structure collapsed during a tornado in 2003.

Situated in the west of Bosnia on the border with Croatia, Objekat 505, as it was officially known, was the largest underground airport in the Balkans. The primary purpose of the Objekat 505 was to house a long-range radar early warning system, akin to NORAD, as well as to provide a strategic command center for the country’s defense.

The Barbados HARP Gun, was part of Project HARP, short for High Altitude Research Project, which was a joint project of the United States Department of Defense and Canada's Department of National Defence created with the goal of studying ballistics of re-entry vehicles at low cost; whereas most such projects used expensive and failure-prone rockets, HARP used a non-rocket spacelaunch method based on a very large gun to fire the models to high altitudes and speeds.

Prora, also known as the Colossus of Prora, is an enormous building complex on the island of Rügen, Germany, that was built by Nazi Germany between 1936 and 1939 as a beach resort of the Strength Through Joy (Kraft durch Freude or KdF) project.

Presidio Modelo (Model Prison) was a former “model prison” of Panopticon design, located on the Isla de la Juventud in Cuba, built between 1926 and 1931, during the repressive regime of Gerardo Machado.

The complex contains over five hundred nuclear-hardened concrete military bunkers, partially buried underground and protected by thick berms of earth, to resist a surface blast wave, as well as radioactive fallout.

ATLAS-I is world’s largest wood and glue structure designed to test the radiation hardening of strategic aircraft systems against EMP pulses from nuclear warfare.

The Kola Superdeep Borehole was a scientific project undertaken by the Soviet Union in the 1970s to better understand the Earth’s crust.

The Space Power Facility (SPF) is the world’s largest vacuum chamber measuring 30 meters tall and 37 meters across.

Antarctic Basecamp, 1911 Tinned ham and whisky are stacked on the shelves beside jars of olives and anchovy paste, awaiting the return of the man who put them there. However, he never would step back into this cosy living space and enjoy the food he had left behind. His name was Robert Falcon Scott – […]

The norias of the ancient Syrian city of Hama are seventeen historic waterwheels located along the Orontes River that date back to the Byzantine Era.

The Post Office Railway, known as Mail Rail since 1987, is a driverless underground railway that was built to move mail between sorting offices.

The unfinished obelisk is the largest known ancient obelisk and is located in the northern region of the stone quarries of ancient Egypt.

In 1948, a top-secret biological weapons laboratory, nicknamed Aralsk-7, was established here. Until its closure in the 1990s, the laboratory tested some of the deadliest pathogens known to man, including plague, anthrax, smallpox, brucellosis, tularemia, botulinum and Venezuelan equine encephalitis.

Kupari was once a hugely popular holiday resort, until it was damaged during the Croatian War of Independence.

The Cultybraggan camp is one of the last remaining World War 2 Prisoner of War Camp in the UK.

Tucked away in the Caucasus Mountains in the north of Georgia, is the historic province of Khevsureti.

Some 250 million years ago, a part of Ukraine was under a shallow ocean. When the ocean dried up, it left behind a huge deposit of salt.

Riese is the code name for a construction project of Nazi Germany in 1943–1945, consisting of seven underground structures located in the Owl Mountains and Ksiaz Castle.

The Berlin Wall was a guarded concrete barrier that physically and ideologically divided Berlin from 1961 to 1989.

The Kelvedon Hatch Secret Nuclear Bunker at Kelvedon Hatch, in the Borough of Brentwood in the English county of Essex, is a large underground bunker maintained during the cold war as a potential regional government headquarters.

In 1959 it was the centre of project Military Atomic Energy Authority operation orpheus investigating the possibility of masking the seismic signal given out by underground nuclear tests.

In the early l950s, RAF Barnham was selected for development as a dedicated storage and maintenance facility for nuclear weapons, in particular for Blue Danube, Britain's first nuclear bomb.

Known as ‘Glass Beach’, for many years the coastline looked the opposite of a pristine and perfect beauty spot. It was a Soviet era tip, where truckloads of broken vodka bottles and cracked porcelain were dumped. Over many years, the waves smoothed away the sharp edges as it turned the shards of glass and china over in the water. They have now become a tourist attraction on Ussuri Bay, near the naval port of Vladivostok in the east.

Danish artist Thomas Dambo has been building stuff using trash and recycled materials since an early age, starting with smaller sculptures such as birdhouses and furniture to bigger pieces such as the six “Forgotten Giants” he recently installed around Copenhagen.

Under the foundation of Phoebe Hearst Memorial Hall at Oglethorpe University in Georgia, the United States, is a large room, that was sealed shut with a welded stainless steel door more than seventy five years ago.

About twenty kilometers from the city of Boulogne-sur-Mer, near the hamlet of Mimoyecques, in northern France, lies a once-secret underground Nazi base.