A chain of three cenotes, an hour by bus or car from Merida, in Yucatan.
My suggestion
If you have a limited budget, you can go to Homun which is nearby, and you can bathe in the cenotes there (cheaply and alone), one of which is actually in someone's garden!
Mexico is brimming with natural and cultural treasures for those visitors keen to discover the country's authentic side. There's no shortage of UNESCO World Heritage sites, and many breathtaking landscapes to be discovered. Let's turn our attention now to the south of the country, to Sian Ka'an, where a reserve of the most incredible biopshere, run by women, is tucked away.
Keen to discover the northern region of Mexico? The Nuevo León, as well as Coahuila are two regions housing cities to see, when going on a visit to the north of Mexico. In fact, Monterrey and Saltillo have several attractions.