Once they were at the heart of the Communist empire, now they lie abandoned leaving only memories of a time before the fall of the Berlin Wall. Now, each haunted shell is ready to reveal its own story.

Still standing today, a fierce-looking prison and an innocuous looking office building in Berlin were actually the headquarters of a feared and ruthless organisation - the Stazi. Also, a covert Communist base hid Cold War submarines for Tito, the former leader of Yugoslavia on the island of Vis. A seemingly innocuous sports centre hides a sinister underground bunker.

And the former HQ of the Soviet Army in East Germany was a forbidden Soviet city within a city - the vast site in the East of Berlin is still abandoned today but its architecture still impresses and even the statues of Lenin still stand in this visually remarkable, place from another time.