In the Puuc Hills region of the Yucatan ruins exhibiting a unique architectural style can still be viewed. The Puuc-style--carefully cut veneer stones set into a concrete core--improved on the earlier practice of setting rectangular stones into a mud or lime mortar. The continued existence of large scale, Puuc-style construction projects, such as those found at Chichen Itza, are testament to the quality of Mayan engineering and craftsmanship.