Tulum holds the honor of being the most picturesque archaeological site in the Riviera Maya and the only one to have been built overlooking the ocean. A visit here offers spectacular views of the Riviera Maya beaches, Caribbean Sea and surrounding coastal region. Tulum was an ancient Mayan fortress city that rose to power toward the end of the Classic period. The most iconic of its structures, the Castillo, is perched on the edge of a cliff overlooking the clear turquoise blue waters of the sea.