Rio [1]’s most magnificent example of baroque architecture is the 17th-century Igreja do Mosteiro de São Bento (Rua Dom Geraldo 68, Centro, tel. 21/2291-7122, 8–11 a.m. and 2:30–6 p.m. daily, R$7 guided visit), near Praça Mauá. The austere facade masks a startlingly lavish interior featuring delicately carved naves and columns, and altars embellished with angels and cherubs that are covered in gold dust. The painted panels are exceptionally fine.
On Sunday mornings, arrive early to take part in the 10 a.m. mass, in which the Benedictine monks chant Gregorian hymns accompanied by the church organ.
Links:
[1] http://www.moon.com/destinations/brazil/rio-de-janeiro/rio-de-janeiro-city