Oaxaca (wah-hah-kah) is famous for its green building stone and for its own particular style of colonial architecture -- an adaptation to the frequent earthquakes that plagued the city in colonial times and still occasionally shake things up. Building walls and facades are thick and broad with heavy buttressing, colonnades are low and spaced closely, and bell towers are squat with relatively wide bases. The cumulative impression of this architectural style is one of mass and substantiality.