In the far northeast of the island. Building started in 1545 as a defense for maritime traffic of Portuguese in the spice route and the market for slaves, gold and ivory. It was attacked by pirates and Dutch, Arabs, Turks and French. Inside is the chapel of Nossa Senhora do Baluarte, of 1522, the oldest Catholic building in Mozambique. The sailors prayed there to thank divine protection during the long sea voyage. Outside is the Dugong Dive Center, to drink a soft drink and relieve heat.