Cenotes are freshwater sinkholes or caves that you can snorkel and dive in. Natural wonders found throughout the Yucatan, several are located along route 307. A rental car will come in handy or you can arrange transportation through your hotel. Private companies on location at the cenotes arrange for guides, gear, and safety precautions; you can't go it alone. The best ones are Cenote Yax Mul, Dos Ojos, El Jardin del Edén, Tres Bocas, and Gran Cenote.
Tulum has some of Mexico's best ruins, perched on a cliff in the archaeological zone. The remains of a walled Mayan city that once served as a port, the three main sites are El Castillo, the Temple of the Frescoes, and the Temple of the Descending God. There are lots of stairs to climb, small entrances for kids to funnel through, and beautiful ocean views. Kids will love spotting the iguanas. For a treat, have the terrific coconut ices sold outside the entrance gate.
Commercialized nature resort where you can snorkel in underground rivers, swim with dolphins and manatees, and visit Mayan ruins. Especially good for families.
Commercialized nature resort with snorkeling and a fantastic river to swim or float down. Be warned: It's a long way to swim. Get there early to beat the crowds.