Mayan for "water stirred by the wind," Cobá flourished from AD 800 to 1100, with a population of as many as 55,000. Now it stands in solitude, and the jungle has overgrown many of its buildings—the silence is broken only by the occasional shriek of a spider monkey or the call of a bird. Most of the trails here are pleasantly shaded; processions of huge army ants cross the footpaths as the sun slips through openings between the tall hardwood trees, ferns, and giant palms. Cobá's ruins are spread out and best explored on a bike, which you can rent for MX$100 a day. Taxi-bike tours are available for MX$200 for an hour and 20 minutes or MX$300 for two hours. If you plan on walking instead, expect to cover 5 to 6 km (3 to 4 miles).
The main groupings of ruins are separated by several miles of dense vegetation. It's easy to get lost here, so stay on the main road, wear comfortable shoes, and bring insect repellent, sunscreen, and drinking water. Inside the site, there are no restrooms and only one small hut selling water (cash only). Don't be tempted by the narrow paths that lead into the jungle unless you have a qualified guide with you.
The first major cluster of structures, to your right as you enter the ruins, is the Cobá Group, whose pyramids are around a sunken patio. At the near end of the group, facing a large plaza, is the 79-foot-high temple, which was dedicated to the rain god, Chaac. Some Maya still place offerings and light candles here in hopes of improving their harvests. Around the rear, to the left, is a restored ball court, where a sacred game was once played to petition the gods for rain, fertility, and other blessings.
Farther along the main path to your left is the Chumuc Mul Group, little of which has been excavated. The principal pyramid here is covered with the remains of vibrantly painted stucco motifs (chumuc mul means "stucco pyramid"). A kilometer (½ mile) past this site is the Nohoch Mul Group (Large Hill Group), the highlight of which is the pyramid of the same name, the tallest at Cobá. It has 120 steps—equivalent to 12 stories—and shares a plaza with Temple 10. The Descending God (also seen at Tulum) is depicted on a facade of the temple atop Nohoch Mul.
Beyond the Nohoch Mul Group is the Castillo, with nine chambers that are reached by a stairway. To the south are the remains of a ball court, including the stone ring through which the ball was hurled. From the main route, follow the sign to Las Pinturas Group, named for the still-discernible polychrome friezes on the inner and outer walls of its large, patioed pyramid. An enormous stela here depicts a man standing with his feet on two prone captives. Take the minor path for 1 km (½ mile) to the Macanxoc Group, not far from the lake of the same name.