Perhaps the most photogenic swimming hole in the Yucatán, the remarkable Cenote X’keken, also called Dzitnup like the nearby village, is 7km west of Valladolid on Hwy-180 libre. Visitors descend through a cramped tunnel into a huge vaulted cave, where a nearly circular pool of crystal-clear turquoise water glows under a shaft of light from an opening in the ceiling. A swim in the ice-cold water is a fantastic experience. Across the road, at the even more impressive (thanks to spooky natural lighting) Cenote Samula, the roots of a huge tree stretch down into the pool.
Colectivos run to the village of Dzitnup from outside the María Guadalupe hotel in Valladolid (M$15). Any westbound second-class bus will drop you at the turn-off, 5km from Valladolid; then it’s a walk of 2km down a signed track. You could also take a taxi or, best of all, cycle from Valladolid on the paved bike path; the most scenic route is down Calle 41-A to San Bernardino, then along Calle 49, which eventually connects to Avenida de los Frailes, then the old highway and the ciclopista.