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

Exploring a crumbling hospital complex in Germany that became the site of unspeakable atrocities and a sprawling Texan farmstead with a hellish reputation.

Exploring two ornate buildings in Texas that were once at the heart of the Mexican Revolution and a top-secret facility outside Berlin, used by a ruthless dictator to escape justice.

Exploring a palatial ruin in Philadelphia built from the riches of an industrial golden age and a country palace in Poland, the scene of a honey-trap devised to ensnare Napoleon.

Exploring a concentration camp in the Czech Republic used for a publicity stunt to fool the world and a stark facility that once housed Oscar Wilde.

Exploring a nuclear-armed facility in Arkansas that served as America's last line of defence in the Cold War and an industrial relic in Wales that felt a young Winston Churchill's wrath.

Exploring derelict villas in Sicily that reveal the island's complicated history with the Mafia and an aristocratic mansion in Ireland embroiled in a bizarre terrorist plot.