The most rewarding day trip is to Abomey (about two hours north), the former capital of the Kingdom of Dahomey. The royal palaces — a UNESCO World Heritage Site — are partly ruined but still extraordinary; the bas-reliefs depict the bloody rise of one of West Africa's most militarised pre-colonial states. Many of the slaves shipped from Ouidah were captured in Dahomey's wars and sold by its kings.
Closer by, the stilt-village of Ganvié on Lake Nokoué is reached from Abomey-Calavi (between Ouidah and Cotonou). Tens of thousands of Tofinu people live in wooden houses standing in two metres of water — a working community, not a museum, accessed entirely by pirogue.
The beach village of Grand-Popo, an hour west, makes a calmer overnight than Ouidah itself, with low-key beachfront guesthouses and far less traffic.