David Cameron was guided around Martyrs' Square by youth worker Abdurahman - who fought against Gaddafi - and Mervat.
Mervat and the organisation she set up, 3 Generation, tries to find information on those who went missing during the dictator's reign and the revolt.
Earlier, the Prime Minister toured a police training centre on the outskirts of Tripoli. He told police recruits it was "very good to be back".
Mr Cameron is due to hold talks with counterpart Ali Zeidan and President Megarief while in the country.