Fortaleza de Santa Teresa, Fortified colonial structure in Rocha Department, Uruguay

Fortaleza de Santa Teresa is a Spanish-built fortification with an irregular pentagonal plan and lance-shaped bastions at each corner, in the Vauban style. Its double granite masonry walls enclose a perimeter of 642 metres, with internal platforms and ramps linking the artillery levels. It stands on a rocky elevation 58 metres above sea level beside the old Camino de la Angostura.

Portugal founded the fort in 1762, naming it after Saint Teresa, a saint especially venerated by Count of Bobadela. Spain took the unfinished works in April 1763 and rebuilt them larger; the present pentagon was designed by French engineer Bartolomé Howel and built between 1765 and 1775, with repairs in 1775 and 1797. The Treaty of San Ildefonso (1777) confirmed Spanish possession.

The name Santa Teresa was chosen by the Portuguese commander Tomás Luís de Osório in 1762, because the saint was a particular devotion of Gomes Freire de Andrade, Count of Bobadela. Inside, the kitchen recreates the soldiers' daily life with a menu of the period, and the rooms display a collection of arms and scale models of Uruguay's historic fortresses.

The fortress stands on a rocky rise 58 m above sea level, beside Route 9, the old Camino de la Angostura, which separates it from the Laguna Negra about 2 km west; the Atlantic is roughly 2 km away. The site lies within Santa Teresa National Park, and its installations, including the weapons collection and models of Uruguayan fortresses, are open to public visiting. The terrain is uneven, with ramps linking the different levels inside the walls.

The fortress was used as a prison from 1895, after decades of abandonment in which its stones were looted and wind-blown sand nearly buried it. From 1927 a commission of architects Baldomir and Capurro and historian Horacio Arredondo led its recovery, replanting the surroundings to hold back the dunes.