Classis Britannica - Ports and Harbours

Ports and Harbours

It was originally believed that the main base of the fleet was in Richborough but more recent archaeological work has uncovered one of only three surviving forts occupied by the fleet's marines at Dover, suggesting this was in fact a major base of the Classis. It may even have been its primary base, though one of the other surviving fleet forts, at Boulogne-sur-Mer, is far larger and thus said by some to be a more likely contender than Dover for that role. Portus Adurni (which was later adapted and known as Portchester Castle) at the north of Portsmouth harbour is another contender and believed to have been at the very least a major base for the fleet.