The Wieliczka Salt Mine is a subterranean network of man-made tunnels up to 327 metres in depth for extracting salt, located beneath the town of Wieliczka in southern Poland.
The Dovbush Rocks is a group of natural and man-made structures, carved out of rock in the Skolivski Beskydy National Park in the Skole Raion of Ukraine.
Camlet Moat is a quadrangular moated enclosure monument known as ‘London’s Camelot’ near the summit of Ferny Hill, located in the Trent Country Park in the London Borough of Barnet.
The Lapis Niger is an ancient sanctuary and a remnant of the Comitium in Rome, that some Romans believed was the venerated sacred tomb of the city’s legendary founder, Romulus.
The Saint-Nazaire submarine base is a large, fortified submarine base constructed by the Germans in the occupied city of Saint-Nazaire on the west coast of France.
The Führerbunker was a subterranean bunker complex in Berlin, Germany, that served as Hitler's final Führer Headquarters in the last months of the Second World War.
The West Norwood Catacombs is a network of subterranean vaults and passages for the burial of human remains beneath West Norwood Cemetery, in London, England.
Stabiae was an ancient Roman town and seaside resort near Pompeii, that was largely buried during the AD 79 eruption of Mount Vesuvius in present-day Italy.
Coria, also called Corioritum and Corbridge, are the remains of a Roman town and fort, located south of Hadrian's Wall at the intersection of Dere Street and the Stanegate, in present-day England.