A UNESCO World Heritage Site. During the Early Classic Period (A.D. 250-600) Calakmul (the Snake Kingdom) emerged as one of four major city states in the Peten region. It maintained a lengthy and intense rivalry with Tikal, 62 miles to the south. Like many other visitors, I became quite focused on the abundant wildlife inhabiting the beautiful subtropical forest which has overtaken the site since its abandonment centuries ago. Troops of howler and spider monkeys were swinging through the trees. Keel-Billed Toucans, Plain Chachalacas, Brown Jays and various other bird species were heard and seen. Intense heat and very high humidity (as well as rain) can limit one's ability or desire to explore the ruins' central core, which extends over an area of 10 square miles. Numerous photos, as well as written documentation of the site's extensive archaeological investigations, are available on the Web. The aerial views are particularly striking. State Of Campeche, Mexico.