Cobá Ruins are 43 km (27 mi.) n.w. of Tulum via the paved, well-marked road (Mex. 109) that branches off Mex. 307 just n. of Tulum and runs n. to Mex. 180 (near Valladolid); follow signs to the ruins entrance. Spreading east from the shore of a lagoon just outside the small town of the same name, this city/ceremonial center dates from between A.D. 600 to 900—older than both Chichén Itzá and the Tulum ruins—and at its height may have supported as many as 50,000 inhabitants.
Excavations began in earnest in the early 1970s. It is believed that as many as 6,500 structures exist. Temples, pyramids and elaborately carved stela (vertical stone tablets) are surrounded by palm tree thickets, tropical hardwoods and roping vines. Cobá has a much more primeval feel than other Yucatán ruins, increasing its sense of mystery.
Nohoch Mul (“large hill”), a 138-foot-high pyramid towering above the flat landscape (about a half-hour walk from the site entrance), is the tallest structure of its kind in the northern Yucatán—rising even higher than the Pyramid of the Magician at Uxmal. It can be climbed; hold onto the rope that runs up one side. The Cobá Group, a cluster of ruins on the right after you enter the site, contains another massive pyramid, the Temple of the Churches (Templo de las Iglesias). Climbing is permitted on the lower levels of many structures, but some sections are blocked off; heed the signs that prohibit climbing.
Bicycle taxi guides can be hired at the entrance, and bikes are available for rent. A bike is the best way to see these ruins; get here early enough and you'll practically have the place to yourself.
Note: If you're not part of an organized tour group, arrive as early as possible to avoid the hordes of tour buses that start showing up between 10 and 11 a.m. The heat, humidity and mosquitoes can be formidable; wear sturdy walking shoes and bring insect repellent and drinking water.