There are more than 60,000 documented sites in the Maya world, which encompasses the five states of Mexico's Yucatán Peninsula and also the countries of Guatemala, Honduras, Belize and El Salvador. These sites range from small villages, which were home to just a few inhabitants, to large cities with populations that topped 70,000.
It is located deep in the heart of the Calakmul Biosphere Reserve, a 1.8 million acre patch of wilderness home to jaguars, howler monkeys, vultures, and hundreds of varieties of birds, butterflies, and plants. Again, like all the other Campeche sites, there are just a handful of people exploring the remains of this extraordinary Maya ghost town.
With the number of buildings - big and small, covered and uncovered - it's not a great stretch of the imagination to see that Calakmul was once a place of great influence.
By the time the Spanish came on the scene at the beginning of the 16th century most Maya cities were either abandoned or in serious decline.
There is no single theory as to why this happened. Ideas range from famine, to revolution to disease, but whatever the circumstances the Maya themselves never disappeared. They are here in today's Yucatán, in every face of every taxi driver, hotel clerk and police officer. Thankfully the language, customs and architectural evidence of their place in history still survive.