The National Mask Museum occupies a handsome late 19th-century building on the Plaza del Carmen and holds one of Mexico's finest collections of ceremonial masks — over 1,300 pieces representing pre-Hispanic, colonial, and contemporary traditions from across the country. It is consistently underrated compared to the city's churches, but is genuinely worth an hour or more.
The collection is organised thematically rather than geographically, which rewards wandering: devil masks from Guerrero sit near deer dance headdresses from Sonora and Carnival masks from Veracruz. The masks are not inert objects under glass — detailed explanatory panels describe what each mask does, what ceremony it belongs to, and what character it portrays. The building itself, a former private palace, has attractive tiled floors and a courtyard.