Calakmul (also Kalakmul and other less frequent variants) is a Maya archaeological site in the Mexican state of Campeche, deep in the jungles of the greater Petén Basin region. It is 35 kilometres from the Guatemalan border. Calakmul was one of the largest and most powerful ancient cities ever uncovered in the Maya lowlands. Calakmul was a major Maya power within the northern Petén region of the Yucatán of southern Mexico. Calakmul administered a large domain marked by the extensive distribution of their emblem glyph of the snake head sign, to be read "Kaan". Calakmul was the seat of what has been dubbed the Kingdom of the Snake or Snake Kingdom. This Snake Kingdom reigned during most of the Classic period. Calakmul itself is estimated to have had a population of 50,000 people and had governance, at times, over places as far away as 150 kilometers. There are 6,750 ancient structures identified at Calakmul; the largest of which is the great pyramid at the site. Structure 2 is over 45 metres high, making it one of the tallest of the Maya pyramids. Four tombs have been located within the pyramid. Like many temples or pyramids within Mesoamerica the pyramid at Calakmul increased in size by building upon the existing temple to reach its current size. The size of the central monumental architecture is approximately 2 square kilometres and the whole of the site, mostly covered with dense residential structures, is about 20 square kilometres. Throughout the Classic Period, Calakmul maintained an intense rivalry with the major city of Tikal to the south, and the political manoeuvrings of these two cities have been likened to a struggle between two Maya superpowers. Rediscovered from the air by biologist Cyrus L. Lundell of the Mexican Exploitation Chicle Company on December 29, 1931, the find was reported to Sylvanus G. Morley of the Carnegie Institute at Chichen Itza in March 1932.