104km (65 miles) SW of Felipe Carrillo Puerto; 37km (23 miles) NW of Chetumal

On a sunny day, you will see why Laguna Bacalar is nicknamed Lago de los Siete Colores (Lake of the Seven Colors): The white sandy bottom turns the crystalline water pale turquoise in shallow areas, morphing to vivid turquoise and through a spectrum to deep indigo in the deeper center. Colors shift with the passing of the day, making a mesmerizing backdrop.

Considered Mexico's second-largest lake, Bacalar is actually a lagoon, with a series of waterways leading eventually to the ocean. Fed not by surface runoff but by underground cenotes, it is almost 50km (31 miles) long. You'll glimpse the jewel-toned water long before you reach the town of Bacalar, about two-thirds of the way down, where you must go for swimming or kayaking.

The town of Bacalar is quiet and traditional, though it seems every year brings a new cadre of expats looking for a different kind of life. There's not a lot of action in town, but you shouldn't miss the Fuerte San Felipe Bacalar, built in 1733 to protect the Spanish from the pirates and Maya rebels who regularly raided the area. Admission is 52 pesos. Overlooking the lake on the eastern edge of the central plaza, the fort houses an excellent museum devoted to regional history, with a focus on the pirates who repeatedly descended upon these shores.

As if to prove the water gods smile upon Bacalar, Mexico's biggest and deepest cenote is less than 2km (about a mile) south of town, at Km 15. Measuring 185m (607 ft.) across, Cenote Azul is surrounded by lush flowers and trees, and filled with water so clear that you can see 60m (200 ft.) down into its nearly 91m (300-ft.) depth.

Some lovely inns dot the lagoon's western shore, which makes Bacalar an appealing alternative base to Chetumal for exploring the Maya ruins in the nearby Río Bec area.