Taking a Sunday stroll through the streets of the relatively posh northeastern Berlin district of Hohenschönhausen (literally “high pretty houses”) in the late 1990s, I come across attractive neighborhoods once inhabited by the East German elite: the generals and high-ranking officers of the Ministry for State Security. Bourgeois-looking bungalow-style houses surround an inviting lake called Obersee. South of the Obersee district, modern, bright, steel-and-glass-style apartments have replaced old socialist housing. A particularly attractive apartment complex overlooks a well-kept cemetery, but the grounds have an unusual bulge in the center. Was this where bunkers hid the workshops and offices of the Stasi's technical division? I peer down one of the shafts and still have not found what lies beneath. Circling to the road I see a big gaping hole – the entrance to an underground parking garage.

It is hard to imagine that during the Cold War this area housed an enormous printing press that produced forged documents and that houses across the street from the peaceful cemetery were really workshops for developing Q-like technology for agents sent on secret missions to the West. By the time Western intelligence arrived on the scene, the printing presses had mysteriously disappeared.

About a mile east of the cemetery, after traveling first on cobblestoned streets, then onto the Freienwalderstrasse, there is a more ominous-looking set of buildings with courtyards: the feared and hated Hohenschönhausen Stasi prison is the most prominent, with its watchtowers, high cement walls, and barbed wire.