The only building which has been preserved from the ancient urban fabric of Tripoli, Oea in antiquity, is the Triumphal Arch. By considering Arab sources, we may shed new light on its evolution, the place it had been in the past and the way it was considered during those times. If we compare two excerpts from Arab-Muslim historiography, written by local travellers, with Western testimonies, we see that the monument was reinterpreted in the light of the new culture which was established in the region and of the local history of the city.