Mexico Guide
The Yucatán
Cobá
Set in muggy rainforest 50km northwest of Tulum, the crumbling ancient city of COBÁ (daily 7am–6pm; M$45) is a fascinating and increasingly popular site. The clusters of buildings are spread out over several kilometres, so the area can absorb lots of visitors without feeling crowded, and you can ramble through the forest in peace, looking out for toucans, egrets, coatis and myriad tropical butterflies, including the giant iridescent blue morpho. A visit here requires at least a couple of hours; renting a bicycle just inside the site entrance (M$25) is highly recommended. Although the ruins aren't as well restored as those at Tulum, their scale is much more impressive, and the dense greenery and wildlife make a good counterpoint to the coast.
Ceramic studies indicate that the city was occupied from about 100 AD up until the advent of the Spanish – the site is even mentioned in the Chilam Balam of Chumayel, a book of Maya prophecy and lore written down in the eighteenth century, well after the city had been abandoned. The city's zenith was in the Late Classic period, around 800 AD, when most of the larger pyramids were built and its wealth grew from links with the cities of Petén, in lowland Mexico and Guatemala. These cities influenced Cobá's architecture and use of stelae, typically seen only in the southern Maya regions. Cobá also prospered later through its connections with coastal cities like Tulum, and several structures reflect the style found at those sites.
The centrepiece of the site is the giant pyramid Nohoch Mul, taller than El Castillo at Chichén Itzá and, in its narrow and precipitous stairway, resembling the pyramid at Tikal in Guatemala; at the top, a small temple, similar to structures at Tulum, dates from around 1200. The view takes in nearby lakes, as well as the jungle stretching uninterrupted to the horizon.
If you're feeling intrepid, head 1km down a shady sacbé to Grupo Macanxoc, a cluster of some twenty stelae, most carved during the seventh century AD. Stele 1 shows part of the Maya creation myth and the oldest date recorded in the Maya Long Count calendar system, which tracks the days since the moment of creation. Other stelae depict a high number of women, suggesting that Cobá may have had female rulers. Clambering between the carvings, you're crossing not natural hills, but unreconstructed buildings; in a way, these offer a more palpable sense of the civilization that thrived here than some of the more immaculately rebuilt structures.
If you turn right at the traffic circle a few kilometres before Cobá (follow signs for Nuevo X-Can), after 18km kilometres you will reach the Reserva de Monos Arañas de Punta Laguna, which since 1994 has been a site for the observation of one of the northernmost populations of spider monkeys. From the reserve's entrance kiosk, you're required to hike with a guide (M$30 per person, plus M$150 for a guide for a group of up to ten people) to where the monkeys usually congregate – there's no guarantee you'll see them, but they're at their liveliest in the early morning and late afternoon.
Four buses a day run to Cobá from Tulum and continue on to Valladolid. The first one leaves Tulum at 7.30am (arriving at 8.30am), and the next, which continues to Chichén Itzá after stopping in Valladolid, arrives in Cobá at 11am – you could therefore theoretically cover both sites via public transport from Tulum, though you would be very rushed. Five buses run back to Tulum from Cobá, the last leaving at 6.30pm. A taxi from Tulum to Cobá costs about M$250 each way.
The village of Cobá, where the bus stops, is little more than a cluster of houses and cabañas a few hundred metres from the site entrance, which fronts a small lake (it's filled with crocodiles; don't swim). Hotels are few, but two are quite comfortable: Villas Arqueológicas (US 
1-800/258-2633; Price: M$750-1100), overlooking the lake, offers a modest bit of luxury, complete with a swimming pool and an archeological library; the Hotelito Sac-bé ( 984/879-9340; Price: M$200-250), on the south side of the main street through the village, is leagues better than the other budget option in town, with five clean rooms offering various amenities (one has a/c). Enquire at the post office across from the bus stop if no one's at the hotel. There's a good restaurant in front of the lake, La Pirámide, which serves Yucatecan specialities.