Tulum
Perched dramatically on seaside cliffs jutting off of Mexico's Yucatan Peninsula, the ancient ruins of Tulum once overlooked an important pre-Columbian port. Its most prominent structure, known for years as El Castillo, was most likely not a citadel but rather an ingeniously designed navigational beacon, so situated that the view of the lamps in its windows told sailors how and when to work their craft safely through the reefs.
