Overview
Cenotes are sinkholes into the limestone aquifer that runs under the whole Yucatán, and there are thousands; the Maya regarded them as entrances to the underworld and drew their water from them. Gran Cenote is two open pools linked by a cavern you can swim through, with stalactites reaching the surface. Sunscreen is banned in the water because it damages the cave ecology, and the rule is enforced at the entrance with a compulsory shower.
Highlights
Arrive at opening: the pools are small, numbers are capped, and by ten it is a queue. Bring a mask — the visibility is the point and the turtles are on the bottom. Cash only at most cenotes, including this one, and the price has risen steeply in recent years.