Riachuelo, Museum ship in Rio de Janeiro, Brazil

The Riachuelo (S22) is an Oberon-class submarine, now a museum ship at the Navy Cultural Centre in Rio de Janeiro. Its 89.9-metre dark grey hull floats beside a concrete pier, with a flat-topped black sail marked "S22" in red and a retractable bow plane forward of it. Eight 533 mm torpedo tubes, two of them aft, were fitted when it was in service.

Built by Vickers at Barrow-in-Furness as the second of three Oberon-class boats, Riachuelo was laid down in 1973 and launched on 6 September 1975. She joined the Brazilian Navy in 1977 and served for two decades, sailing over 181,000 nautical miles in 1,283.5 days at sea. Decommissioned on 12 November 1997, she is now a museum submarine at the Navy Cultural Centre in Rio de Janeiro.

The submarine is named after the Battle of Riachuelo, a key naval conflict during the Paraguayan War that demonstrated Brazil's maritime power. This name links modern defense technology to an important moment in Brazilian naval history.

The submarine is moored at the Espaço Cultural da Marinha in Rio de Janeiro's historic centre, so it is reached on foot from nearby Praça XV. Visitors go aboard the hull and look into the torpedo tubes and cramped crew spaces; the deck and hatches are narrow, so wear flat shoes.

Riachuelo was the first submarine of its class to receive high-capacity batteries made in Brazil by Saturnia, using German technology, fitted during a repair period in 1984. Look for the red "S22" painted on the side of the sail.