Four kilometers (2.5 miles) west of Valladolid on Highway 180 is the small community of Dzitnup, home to two appealing underground cenotes. Both make for a unique and refreshing swim—in fact on warm days both can be somewhat crowded. At both cenotes, there are parking lots and many small artesanía stands at the entrance, and you’ll be aggressively pursued by children offering to watch your car or sell you a postcard.

Although the two are across the street from each other, Cenote X’keken (8 a.m.–6 p.m. daily, US$2.50 adults, US$1.50 under 17, video cameras US$2.75) has been open longer and is better known; many postcards and travel guides show it as “Cenote Dzitnup.”

After a reasonably easy descent underground (in a few places you must bend over because of a low ceiling; there’s a hanging rope to help), you’ll come to a circular pond of clear, cool water. It’s a pretty, albeit damp, place, with a high dome ceiling that has one small opening at the top letting in a ray of sun and dangling green vines. Often an errant bird can be seen swooping low over the water before heading to the sun and sky through the tiny opening. Stalactites and at least one large stalagmite adorn the ceiling and cenote floor.

At Cenote Samula (7 a.m.–5 p.m. daily, US$2.50 adults, US$1.50 under 17, video cameras US$2.75) tree roots dangle impressively from the ground-level roof all the way down to the water. Enter through a narrow tunnel, which opens onto a set of stairs that zigzag down to the water. Fearless kids jump from the first or even second switchback, into the clear turquoise water below.

Many people ride their bikes here—a bike path runs parallel to the highway, making it a pleasant trip. A cab to the cenotes runs about US$5.