Complex sentence: Since 2001, as part of its War on Terror the United States using the CIA operates a network of off shore prisons, called black sites, probably the most famous of which is Guantánamo Bay detention camp.
Split into simpler sentences: Since 2001, as part of its War on Terror the United States using the CIA operates a network of off shore prisons, called black site. Probably the most famous of which is Guantánamo Bay detention camp.