http://playadelcarmeninfo.com/playa-del-carmen-info-mayan-ruins-of-coba.html

About a two hour drive by car from Play Del Carmen, 1 hour from Tulum, Cobá is one of the oldest Mayan settlements on the peninsula Cobá means "waters stirred by the wind". This name is most likely derived from the five lakes in the vicinity. Cobá was a thriving city during the Classic period (600-900 A.D.), although it had been settled for about a thousand years before this. The largest Mayan pyramid at Cobá is Nohoch Mul (large hill). The great pyramid Nohoch Mul stands at 42 meters high and is the tallest of all Mayan structures in the Yucatan Peninsula. Climb the 120 steps, observing that the Maya carved shell-like forms where you put your feet. The view from the top is amazing. You can see many other pyramids that have not yet been excavated due to lack of money. These great pyramids must have took over 100 years to build. The hardest part is walking down.