Exploring traces of a mass deception hidden at Ponte Dirillo in Italy, as well as a once lavish theatre in Ohio and an ancient city with a poisonous secret.

Exploring a grand structure in Hull that was reduced to rubble by Hitler's planes, Casa Albero in Italy, USS Hornet in California and the Sofia tunnels.

Exploring a decrepit Liberian landmark with American origins, a desolate town in Belgium and a pioneering scientific structure in Cleveland.

Exploring Haludovo Palace Hotel in Croatia, Wolf's Lair, a German military complex and Herouni Mirror Radio Telescope - a pioneering facility in Armenia.

A symbol of national pride that became a symbol of excess in the Turkish capital of Ankara.

Exploring Yongma Land - a South Korean dreamland given a second life from the most unlikely of places.

Exploring Old Joliet Prison, a battered facility near Chicago that descended into open war, but then hosted the Blues Brothers!

Exploring Castel Volturno in Campana in Italy, Colorado and HMP Shepton Mallet in Somerset.

Exploring Camp Hero in Long Island, and a salt mine in Poland.

Exploring the ruined site of Troy, that helped decode one of the world's most enduring mysteries.

Exploring Seodaemun Prison, a facility in Seoul that helped spawn a legend known as South Korea's Joan of Arc.

Exploring Opa-Locka City Hall, a strange structure that began as the dream of an American Renaissance man, but soon turned into a nightmare.

We explore Namibia's arid Skeleton Coast, where traces of a brutal but once vital industry lie scattered.

We explore Schindler's Ark in the Czech Republic, a secret refuge in Europe's killing fields, and a lost Amazonian paradise deep in the Brazilian rainforest.

We visit the decaying remains of Old Essex County Jail in New Jersey, a facility that became a powder keg of injustice that was set to explode.

We visit the Polish city of Walbrzych, where a fairytale castle on a cliff conceals a vast subterranean tunnel network linked to a legend of lost Nazi gold.

We explore Fort Sherman, a jungle stronghold in Panama built to defend a prized American possession that soon faced the threat of an elaborate Nazi conspiracy.

Exploring an Oklahoman town so wealthy it inspired a Hollywood film.