Museo de Arte Contemporáneo de Oaxaca (MACO). Quite the beautiful building.

An excerpt from The New York Times about MACO:
...The 18th-century building housing the museum merits a visit for its own sake. It's called the Casa de Cortéz and some say that it was built by order of Hernán Cortéz after he received the title of Marqués of the Valley of Oaxaca. In reality, it was built 2 centuries too late for that.