Tulum ( (Tulu'um in Modern Maya) ; in Spanish orthography, Tulum) is the site of a Pre-Columbian Maya walled city serving as a major port for Cobá.The ruins are located on 12-meter (39 ft) cliffs, along the east coast of the Yucatán Peninsula on the Caribbean Sea in the state of Quintana Roo, Mexico. One of the best-preserved coastal Maya sites, Tulum is today a popular site for tourists.

From wikipedia: http://en.wikipedia.org/wiki/Tulum