The headquarters of Libya's intelligence services - a notorious symbol of Muammar Gaddafis 42-year rule - is now firmly in rebel hands.
Detailed reports on anyone opposing him would come directly to this building. Parts of the compound also served as a prison, with secret cells housing many Libyans that the regime would make disappear.
The building is full of confidential documents that could provide a valuable insight into what was one of the world's most secretive regimes. But it will take weeks to sift through.
Jamal Elshayyal reports from Tripoli in this Al Jazeera exclusive.