To the west of the Vieux Port lies Abbaye St-Victor, the birthplace of Christianity in Marseille, built on a 3rd century BC necropolis. It's €2 to visit the crypts, with guided tours available from 4pm to 6pm on Tuesdays and Thursdays (or download a 'tour' from www.saintvictor.net).
Indirizzo3 rue de l’Abbaye
Orari9am-7pm
Come Arrivaremetro: Vieux Port