The Fortaleza de Santa Cruz da Barra sits on a rocky promontory at the entrance to Guanabara Bay, staring across the water at its companion fort, the Forte de São João on the Rio side. Built by the Portuguese in the 1560s and expanded repeatedly over the following two centuries, it is one of the best-preserved colonial military complexes in Brazil.
Guided tours run daily and take you through the thick stone walls, the dungeons, the cannon batteries, and the chapel. The views across the bay toward Rio are superb. The fort is about 8 km from central Niterói; most visitors combine it with the beaches of Jurujuba, the small fishing community just beyond.