Do not miss.  Not far off of the pay road.  The only ancient Mayan city with 3 dimensional sculptures.  Not crowded.  The city dates to 600BC.  You are allowed to climb the pyramids here, unlike at Chichen Itza, and the tallest pyramid is about 95 feet high, you can see the tops of other pyramids 30 miles away.  There are lots of beautiful birds, monkeys and rabbits.  There is no printed information available, you can hire a guide for 450 pesos. Compared to Coba, Chichen Itza, Ixchel, Tulum, and Xel-Ha and these were by far the best ruins.