A row in Mexico about the construction of museums of chocolate at Chichen Itza, the Mayan complex in the Yucatán peninsula that is a Unesco World Heritage site, and in nearby Uxmal, has revealed deep divisions within the National Institute of Archaeology and History and called into question the institute’s management of such sites.

Opponents of the planned museums, some of whom work for the institute, organised a public campaign that resulted in the institute ordering work to stop on the Choco-Story Museum at Chichen Itza. The chocolate museum was being built on private property but within the site’s protected archaeological zone—around 30 metres from the Great Ball Court of Chichen Itza. Starting construction without a permit breaks a law that protects Mexican national heritage....