Dos Ojos Cenote

Two round cenotes sit side by side here and open into one big shared cavern, the two eyes of the name. The water is so clear that what limits the view is light, not murk. Snorkellers float above stalactites at the edge of the daylight, and certified divers follow a guide through the cavern at five to seven metres, usually two dives of 45 minutes in a day. You can also swim across to the Bat Cave, a neighbouring cenote with bats roosting overhead.

This was the way in for the divers who mapped one of the longest flooded cave systems on earth, and scenes for Planet Earth and an IMAX film were shot here. The water stays at 25°C all year, and near the openings it is no deeper than about ten metres.

It is busy, with a hundred or more people on an ordinary day, so set aside two or three hours. The wider park has other cenotes on the same road (Nicte-Ha with its water lilies, the 120-metre-deep El Pit for divers only, and Jaguar with zip lines and forest trails), plus lockers, bike rental and a restaurant. A small local kitchen at the highway turn-off serves lunch until mid-afternoon.