If you go to Chichenitza, and that is really a must visit site, be sure to check out a small area near one of the non-descript stone buildings which has stone reliefs of all the known animals in the jungle — your guide will know where this is -— on one panel you will see what looks very much like a horse... which as you know was not know to be in the Americas at that time.
Cozumel has a small stone temple or two that legend has was an early warning for hurricanes as it supposedly started making a loud sound when the wind got to a certain speed.