by Matthew Cole and Brian Ross, ABC News

The CIA built one of its secret European prisons inside an exclusive riding academy outside Vilnius, Lithuania, a current Lithuanian government official and a former U.S. intelligence official told ABC News this week.

Where affluent Lithuanians once rode show horses and sipped coffee at a café, the CIA installed a concrete structure where it could use harsh tactics to interrogate up to eight suspected al-Qaeda terrorists at a time.

“The activities in that prison were illegal,” said human rights researcher John Sifton. “They included various forms of torture, including sleep deprivation, forced standing, painful stress positions.”

Lithuanian officials provided ABC News with the documents of what they called a CIA front company, Elite, LLC, which purchased the property and built the “black site” in 2004.

Click here for more and to watch exclusive video.