'On an idyllic lake surrounded by woods and a double row of mesh-and-razor-wire fences about 100 miles north of Warsaw, there stands a secluded villa that the CIA once used to interrogate — and allegedly torture —top al Qaida suspects.

On the grounds of the Polish intelligence-training academy and nicknamed "Markus Wolf" for the former East German spy chief, it’s the focal point for a top-secret probe that Polish prosecutors have launched into how their government tolerated rampant violations of international and Polish law.

If former officials are brought to trial, or if the classified files in the prosecutors’ offices are made public, the result will be revelations about an American anti-terrorism operation whose details U.S. officials are fighting to keep secret.'

Read more: Poland Peels Back Layers on CIA Detention Center