The square that surrounds and is named for the Catedral de la Habana is one of La Habana Vieja's most beautiful spots. In addition to the cathedral, you'll find several elegant mansions that once housed the city's aristocrats.
The Casa de los Marqueses de Aguas Claras (1751–75), in the square's northwestern corner, was built by Antonio Ponce de León, the first Marquis of Aguas Claras and a descendent of the discoverer of Florida, Juan de Ponce de León.
Today the building contains El Patio Colonial, a restaurant whose tables fill a verdant interior courtyard as well as the upper floors. On the square's western edge is the 19th-century Casa de Baños (Bath House), which was built on the spot where an aljibe (cistern) was constructed in 1587. It served as the main municipal water supply and as a public bathing house. The narrow cul-de-sac next to the Casa de Baños is the Callejón del Chorro (Alley of the Water Fountain), named for an aqueduct that ended here in Havana's early days.
Wander along the square's eastern edge for a look at the early 18th-century Casa de Lombillo, the site of Cuba's first post office. A letter drop in the shape of a Greek tragedy mask grimaces from the wall to the right of the main door. Its inscriptions reads: "correspondencia interior y peninsular". In the old days, it seems, you could plop both local and international ("peninsular" mail was being sent to the Iberian Peninsula or Spain) letters in one slot. The building is now home to an education museum, with displays honoring a 1961 campaign in which students and teachers took to the hills to spread literacy.
Directly across the square from the cathedral is the Museo de Arte Colonial, with its rich collection of colonial objects ranging from violins to chamber pots. It's in the Casa de Luis Chacón—also known as Casa del Conde de Bayona after the son-in-law of the original owner—which dates from the 17th century and which saw its first restoration in 1720. A small theater here, La Salita, often has plays and monologues. Calle San Ignacio 61, La Habana Vieja, Havana. 7/862–6440. 2 cuc. Tues.–Sun. 9:30–5:30.