The São Sebastião Museum occupies the Forte de São Sebastião, a 16th-century Portuguese fort at the northern edge of the city waterfront. The fort is the best-preserved colonial structure on the island — a solid, square construction in yellow stone, with corner bastions that look out over Ana Chaves Bay. The lighthouse built into one of its towers still operates.
Inside, the museum covers the island's history from Portuguese settlement through the sugar era, the slave trade, the cocoa boom, and independence in 1975. The displays are modest but the setting is remarkable: thick walls, cool stone corridors, and panoramic views of the bay from the battlements. It is the essential stop in São Tomé town and takes about ninety minutes. A small collection of traditional crafts and colonial-era items fills the upper floors.