Abandoned Engineering

This episode explores Oradour-sur-Glane is a French town drenched in infamy, the victim of a notorious raid; Alcatraz, a facility famed for breakouts, subjected to a daring break-in; and Sealand, a micronation off the English coast, stormed by a band of mercenaries.

The Tunnels of Gibraltar were a Second World War espionage base, hidden in the Rock of Gibraltar, which lay undiscovered for decades; at Atlas-1 Test Site, are the remains of an ingenious US Airforce project that continues to keep us safe; at Roghudi Vecchio is an ancient culture threatened when an Italian town is deserted; and at Naissaar, a highly classified Soviet munitions factory camouflaged in the forests of Estonia.

In the Scottish capital of Edinburgh, hidden from view, a series of vaults tell a murky story of opportunity, crime and destitution; at Fort Schwatka Unalaska are the remains of an Alaskan battleground, where a foreign invader set foot on American soil for the first time since 1812; The Old Herring Factory is a remote Icelandic facility that played a major role in transforming the nation's economy; and in the calm waters of Croatia's Adriatic Sea, Fort Punta is a vast fortress charts the rise and fall of a European empire.

An Appalachian dream that conjured the spirit of the old west, left to rot on a North Carolina mountainside; in the ex-Soviet republic of Georgia are the remains of an ingenious sky-high solution to a ground-based problem, Chiatura, once known as the Venice of the air; Guernsey Hospital was a vast complex built when a slice of Britain lived under the Nazi yoke; and Houtouwan , a Chinese island of simple means, caught up in a brutal revolution that ushered in a tragic period of mass incarceration and murder.

Agdam is a city in Azerbaijan raised to the ground in a conflict decided by a new weapon of war. Plus, a Kansas City Workhouse that appears to have been built for the aristocracy; two seemingly deserted towns in Sicily that are hard to decipher; and an extensive complex in Estonia that helped spawn a revolution.

An industrial ruin in the Florida everglades that once competed in the greatest race humankind has ever witnessed; a community in Indonesia shattered by a terrifying and deadly unseen force; the graffiti covered walls of an Ibizan legend hint at a fun-loving past; and a Bulgarian school that concealed an ambitious and covert plan for revenge.

A once lavish theatre in Ohio that saw the house brought down; an ancient city with a poisonous secret, only recently revealed; a war-torn shell given new purpose by a blockbuster series; and traces of a mass deception hidden across an Italian island.

In the disputed region of Abkhazia lies the wreckage of a vast site that promised heroic sporting victory over western rivals; a dense forest near the Czech capital of Prague hides an eerie castle rumoured to possess supernatural powers; in Liberia, West Africa, the ruin of a luxury hotel taken by a cruel warlord, then transformed into safe haven; and in north-central Arizona, a settlement's scattered remains reveal an ancient community given life by a deadly force.

This episodes visits Serbia, Fort Pike in Louisiana and a mountainside refuge in Georgia, revealed to the world by an act of God.

This episode explores a grand structure in Hull, once the heartbeat of the community, reduced to rubble by Hitler's planes while those inside were laughing at him on the silver screen; Casa Albero in Italy, USS Hornet in California and the Sofia tunnels.

The Whig Party HQ is a decrepit Liberian landmark with American origins; Doel is a desolate town in Belgium that stands in the shadow of its destroyer; Chacaltaya Ski Resort in Bolivia is a high-altitude retreat, once a world-class sporting resort, now drained of its lifeblood by a global threat; and Warner & Swasey is a pioneering scientific structure in Cleveland rendered obsolete by light pollution.

The Dew Drop Inn is a music mecca in New Orleans that dared to take on the authorities and paid the price; Belgica Fort is an epic ruin built to defend the most unlikely of treasures; and the legacy of West-81, a military exercise that terrified the West.