A Maya site on the eastern coast, near the northern tip of the island, the castillo (castle) comprises a lookout tower, the base of a pyramid, and a temple with two chambers capped by a false arch. The waters here harbor several shipwrecks, remnants from the days when buccaneers lay in wait for richly cargoed galleons en route to Europe. It's a fine spot for snorkeling because there are few visitors to disturb the fish.

Chankanaab Parque Natural (Chankanaab Nature Park)

Chankanaab (the name means "small sea"), a 10-minute drive south of San Miguel, is a lovely saltwater lagoon that the government has made into a wildlife sanctuary, botanical garden, and archaeological park. The treasures from the Cozumel Archaeological Park--Toltec, Mexican, and Maya statues and stone carvings--have recently found a new home here. Underwater caves, offshore reefs, a protected bay, and a sunken ship attract droves of snorkelers and scuba divers. The botanical garden boasts about 350 varieties of plant life from more than 20 countries, and scattered throughout are reproductions of Maya ruins and typical living quarters. Some 60-odd species of marine life, including fish, coral, turtles, and various crustaceans, reside in the lagoon; however, a major scientific study is currently under way, so swimming through the underwater tunnels from the lagoon to the bay or walking through the shallow lagoon is no longer permitted. Still, there's plenty to see in the bay, which hides crusty old cannons and anchors as well as statues of Jesus Christ and Chac Mool.

El Cedral

Once the tiny village and ruins comprised the largest Maya site on Cozumel: This was the temple sighted by the original Spanish explorers in 1518, and the first Mass in Mexico was reportedly celebrated here. These days, there's little archaeological evidence of El Cedral's past glory. Conquistadors tore down much of the temple, and at the turn of this century the site was uninhabited. The U.S. Army Corps of Engineers destroyed most of the rest of the ruin during World War II to make way for the island's first airport, and now all that remains is a small structure capped by jungle growth; its Maya arch, best viewed from inside, is covered by faint traces of paint and stucco. Numerous small ruins are hidden in the heavy growth of the surrounding area, but you'll need a guide (there are usually one or two hanging around the main ruin) to find them. Every May a fair, with dancing, music, and a cattle show, is held here. After exploring the ruins, you can take a rest nearby in a small green-and-white cinder-block church, typical of rural Mexico. Inside, a number of crosses are shrouded in embroidered lace. During religious festivals the simple room is adorned with folk art.

Isla de Pasión

Beyond Punta Norte, in the middle of Abrigo Bay, this tiny island is now part of a state reserve. Fishing is permitted and the beaches are secluded, but there are no facilities on the island, and since so few people go, there are no scheduled tours. You'll have to bargain with a local boat owner for transportation if you want to visit.

Laguna Colombia (Colombia Lagoon)

A prime site for jungle aficionados, this lagoon lies at the island's southern tip and is most commonly reached by boat, although there is a trail. Fish migrate here to lay their eggs, and barracuda, baby fish, and birds show up in great numbers in season. There are popular diving and snorkeling spots offshore in the reefs of Tunich, Colombia, and Maracaibo.

Punta Celerain Faro (Punta Celerain Lighthouse)

Located on the southernmost tip of the island, the lighthouse is surrounded by sand dunes at the narrowest point of land. It affords a misty, mesmerizing view of pounding waves, swamps, and scraggly jungle. Alligators were once hunted nearby; nowadays you may spot a soldier or two from the adjacent army post catching an iguana. The point comes to life at midday when the lighthouse keeper serves fried fish and beer, and locals and tourists gather to chat; Sundays are particularly popular. The lighthouse is at the end of a 4-km-long (2-1/2-mi-long) dirt road--you'll need a four-wheel-drive vehicle if you plan to visit.

Punta Molas Faro (Punta Molas Lighthouse)

If you are going to attempt to reach the northernmost tip of the island, be sure you have plenty of time and a reliable four-wheel-drive vehicle. While exploring this area keep alert for possible sightings of crocodiles, boa constrictors, and scorpions. They prefer not to have contact with humans, so it's unlikely that they would interfere with your visit, but the unexpected can happen. The lighthouse is an excellent spot for sunbathing, birding, and camping. Although this entire area is accessible only by four-wheel-drive vehicles or by boat, the jagged shoreline and the open sea offer magnificent views, making it well worth the trip.

San Gervasio

These ruins of the largest existing Maya and Toltec site on Cozumel are worth visiting. San Gervasio was once the island's capital and probably its ceremonial center, dedicated to the fertility goddess Ixchel. The Classic- and Post-Classic-style site was continuously occupied from A.D. 300 to A.D. 1500. Typical architectural features from the era include limestone plazas and masonry superstructures atop stepped platforms, as well as stelae, bas-reliefs, and frescoes. What remains today are several small mounds scattered around a plaza and several broken columns and lintels that were once part of the main building or observatory. Each of the ruins is clearly identified and explained on three-language plaques (Maya, Spanish, and English) and placed in context with individual maps. There are a snack bar and some gift shops at the entrance. To get here take the cross-island road (Av. Juárez) to the San Gervasio access road; follow this road north for 7 km (4-1/2 mi). More likely than not the ruin will close during October.

San Miguel

Cozumel's only town retains the laid-back tenor of a Mexican village, although its streets are dotted with an interesting variety of shops and restaurants. Avenida Rafael Melgar, San Miguel's waterfront boulevard, has a wide cement walkway, called the malecón. The malecón separates Avenida Rafael Melgar from the town's narrow sandy beach. As in most Mexican towns, the main square, here called the Plaza del Sol, is where townspeople and visitors hang out, particularly on Sunday nights when mariachi bands join the nightly assortment of food and souvenir vendors.

Museo de la Isla de Cozumel (Museum of the Island of Cozumel) is housed on two floors of what was once the island's first luxury hotel. Four permanent exhibit halls of dioramas, sculptures, and charts explain the island's history and ecosystem. Well laid-out and labeled displays cover pre-Hispanic, colonial, and modern times and detail the local geology, flora, and fauna. Among the highlights is a charming reproduction of a Maya house. The museum also presents temporary exhibits, guided tours, and workshops. Av. Rafael Melgar between Calles 4 and 6 Norte, 987/21475. Admission: $3. Hours: 10-6