Indiana Jones and Cobá's Lost Tales
Feel like Indiana Jones for a day and visit Cobá ruins, that evoke the spirit of going on an adventure. This is a real ruin site, not manicured. Combine it with Multún Ha cenote, a hidden gem set in secluded rugged jungle just off the Cobá lake. One of my favourite Yucatán trips.
You can absorb the spirit of the jungle as you walk along the winding tracks (reserve around two hours), without big tourist crowds. Or you can hire a bike or a Mayan peddler with a tricycle. The choice is yours. You will see a lot of unexplored ruins alongside a few restored structures and the bonus is the jungle view once you climb the steep and tall Nohoch Mul pyramid (120 steps).
Multún Ha (Hammocks/cenotes)
This cenote is set in a secluded jungle just off the Cobá lake. But once you enter the deep hole in the ground (literally), you will come to a cathedral cave and crystal clear waters with endless visibility. There are basic restrooms and changing rooms but for lunch you will need to go to the Cobá village. There are two restaurants with a buffet lunch right on the lake: La Pirámide and Nicté-Ha. No buses go here; you will need to come by car. The exact driving directions are in my Multún Ha post.
If you have time left or want to squeeze more into one day, you could visit Tulum ruins or stop by at Casa Itzamna just outside the Cobá village. Here you can have a cup of tea and learn about the Mayan garden with medicinal plants and the local melipona stingless bees.
The drive from Playa del Carmen to Cobá takes an hour and a half, or it's 50 minutes from Tulum.