“El Castillo” (the Castle), the largest pyramid at 130 feet above the plaza, has carved friezes on the east and west sides. The frieze on the east has been preserved and covered with a fiberglass replica of the central mask that represents the sun god. It’s flanked by the moon and Venus.
On a clear day, you can see across into nearby Guatemala and near Caracol in the Pine Ridge Mountain Reserve. It’s a site on its own.