In the 1200's, Tulum was an important Mayan seaport along the Yucatan coast. It was the only Mayan city built on a coast. It remained inhabited well after the arrival of the Spanish. El Castillo dominates the site. It is the tallest pyramid at Tulum, standing 24 feet (7.5 meters) tall. Built on a limestone cliff overlooking the Caribbean coast, it served as a lighthouse to guide ships into the port.