The Chichen-Itza Caracol is a round structure, more closely related to the temples of central and eastern Mexico than to known Mayan structures.  However, the continuous molding and Chaac masks are definitely Puuc in style.  The Caracol was built around 909 A.D.  The combination of Mexican design elements and Mayan workmanship represents the cultural transition that was going on during that time, when the Mexicans were becoming firmly established at Chichen-Itza.  The four doorways are aligned with the cardinal directions.  Inside a spiral staircase leads up to windows that line up to view the northerly and southerly extremes of Venus at the horizon.  Other heavenly bodies were tracked by matching their alignment with other features throughout the Caracol.