The terrace of the Chateau de la Citadelle de Bourg en Gironde offers a superb view of the Dordogne just before the junction with the Garonne, from where they form the Gironde estuary. You can still see the facade of the old 18th century charterhouse that was built there, as well as a view of the river.
The Citadel of Bourg museum presents an impressive network of underground passages as well as a collection of horse-drawn carriages. Open daily between June and September.