Plaza de Mayo’s only remaining colonial structure, the Cabildo was a combination town council and prison, and the site where criollo patriots deposed Spanish viceroy Baltasar Hidalgo de Cisneros in 1810. The present structure preserves part of the recova (arcade) that once ran the plaza’s width.

The museum is thin on content—a few maps, paintings and photographs of the plaza and its surroundings, and a portrait gallery from the British invasions (1806–1807) and the Revolution of May 1810. The real star is the building, part of which survived 19th-century mayor Torcuato de Alvear’s wrecking ball (which made the Avenida de Mayo possible).

The Museo del Cabildo (Bolívar 65, tel. 011/4343-4387, US$0.35) is open 11:30 a.m.–6 p.m. Wednesday–Friday, 2–6 p.m. Saturday, and 3–7 p.m. Sunday.