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.

Erta Ale (or Ertale or Irta'ale) is a continuously active basaltic shield volcano in the Afar Region of northeastern Ethiopia. It is situated in the Afar Depression, a badland desert area. Erta Ale is the most active volcano in Ethiopia.

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.

The Stelling van Amsterdam was the most advanced military structure of its type in the world - 135 km (84 miles) of forts, batteries and moats completely encircling the city in a defensive barrier.

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.

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.

Checkpoint Charlie was the name given by the Western Allies to the best-known Berlin Wall crossing point between East Berlin and West Berlin during the Cold War.

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.

Located just over eight hundred kilometers away from the North Pole, the community of Alert, on the northeastern tip of Ellesmere Island, in Nunavut, Canada, is the most northerly permanent settlement in the world.

Unlike other notorious barriers in the world, the Moroccan Wall is rarely in the news and is little discussed outside of Africa. The existence of this wall has been buried in the desert, along with the 40-year-old plight of the Sahrawi people the Moroccan Wall has kept divided.

About 25 miles south of Berlin lies the small town of Wunsdorf, home to about six thousand inhabitants. But less than thirty years ago it had a population of sixty thousand, of which fifty thousand were soldiers of the Red Army. They lived inside one of the biggest military bases in Europe and the biggest […]

Hadrian's Wall was a defensive fortification in Roman Britain, begun in AD 122 during the rule of emperor Hadrian. In addition to its military role, gates through the wall served as customs posts.

Dachau concentration camp was the first of the Nazi concentration camps opened in Germany, intended to hold political prisoners.

Djémila is a mountain village in Algeria, near the northern coast east of Algiers, where some of the best preserved Berbero-Roman ruins in North Africa are found.

Royal Air Force Menwith Hill or more simply RAF Menwith Hill is a Royal Air Force station in England which provides communications and intelligence support services to the United Kingdom and the United States of America. The site contains an extensive satellite ground station and is a communications intercept and missile warning site and has been described as the largest electronic monitoring station in the world.

The Maunsell Forts were small fortified towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom.

The intense secrecy surrounding the base made it the frequent subject of conspiracy theories and a central component to unidentified flying object (UFO) folklore.