Vienna, the elegant capital of Austria, is more than just a city of music and culture. Beneath its sophisticated facade lies a darker secret: it's one of Europe's most significant espionage hubs. With its neutral status and strategic location, Vienna has become a magnet for intelligence agencies worldwide.
According to Bloomberg, an estimated 7,000 secret agents operate among the nearly 17,000 accredited diplomats in the city.
How did this happen? Read on to uncover the secrets of this modern den of spies. Click through the gallery to get started.