The vast northern department of Petén occupies about a third of Guatemala but contains just over three percent of its population. This huge expanse of tropical rainforest, swamps and savannah forms part of an untamed wilderness that stretches into the Lacandón forest and Calakmul reserve of southern Mexico and across the Maya Mountains to Belize. Totally unlike any other part of the country, large expanses of the Petén remain virtually untouched, with ancient ceiba and mahogany trees that tower 50m above the forest floor. The area is extraordinarily rich in wildlife: some 285 species of bird have been sighted at Tikal alone, including a wide range of hummingbirds, toucans, blue and white herons, hawks, buzzards, wild turkeys and the motmot (a bird of paradise). Beneath the forest canopy lurk many other species that are harder to locate. Among the mammals are the lumbering tapir, ocelots, deer, coatis, jaguars and monkeys, plus crocodiles and thousands of species of plants, snakes, insects and butterflies.

In the past few decades, however, this privileged isolation has become increasingly under threat. Waves of settlers have cleared enormous tracts of jungle, while oil exploration and commercial logging have brought with them mountains of money and machinery, cutting new roads deep into the forest. The population of Petén, in 1950 just 15,000, is today estimated at close to 500,000, a number which puts enormous pressure on the remaining forest. Yet despite forty percent of Petén being officially protected as the Reserva de la Biósfera Maya (Maya Biosphere Reserve), regulations are loosely enforced and widely ignored. Today, though there are numerous Petén-based ecological groups committed to preserving the remaining forests, activists are subject to routine threats and protective laws are widely ignored.

Population boom and environmental failure have occurred before in the Petén, and most experts concur that these factors precipitated the collapse of the Classic Maya cities here eleven centuries ago. Petén was both the birthplace and heartland of the Maya civilization, which flourished for almost two thousand years between 1000 BC and the tenth century AD, by which time Maya culture had reached unparalleled architectural, scientific and artistic achievement. Great cities rose out of the forest, surrounded by huge areas of raised and irrigated fields and connected by a vast network of causeways to smaller settlements. But incredibly high population densities and a prolonged drought towards the end of the Classic period (250–909AD) brought about a swift collapse, leaving the forest to reclaim the temples and palaces.

Today the ruins of several hundred ancient Maya sites pepper the region, although many of them still remain completely buried in jungle, and others are known only to locals and looters. In the past few years, satellite imagery has uncovered the remains of two large cities, El Pajaral and Xulnal, while archeological excavations at other near-forgotten sites, including Cancuén, Wakná and Cival, have revealed them to be much larger than originally thought. Tikal and El Mirador are among the largest and most spectacular of all Maya ruins – Tikal alone has some 3000 buildings – but they represent only a fraction of what was once here. At the close of the tenth century the cities were mysteriously abandoned, after which some people moved north to the Yucatán, where the Maya civilization continued to flourish until the twelfth century.

By the time the Spanish arrived the area had been partially recolonized by the Itza, a group of Toltec Maya (originally from the Yucatán) who inhabited the land around Lago de Petén Itzá. The forest proved so impenetrable that it wasn't brought under Spanish control until 1697, more than 150 years after they had conquered the rest of the country. Although the Itza resisted persistent attempts to Christianize them, their lakeside capital was eventually conquered and destroyed by Martín de Ursúa and his army, thus bringing about the defeat of the last independent Maya tribe. The Spanish had little enthusiasm for Petén though, and under their rule it remained a backwater, with nothing to offer but a steady trickle of chicle – the basic ingredient of chewing gum, which is bled from sapodilla trees. Independence saw no great change, and it wasn't until 1970 that Petén became genuinely accessible by car. Even today, the network of roads is skeletal, and many routes are impassable in the wet season.

The Petén forests historically provided shelter for some of Guatemala's guerrilla armies, which led to many of the settlers being driven across the border into Mexico and becoming refugees. Most of the refugees have returned, though small pockets of tension still exist in the region. Many disputes are over land rights, with Belizean troops evicting Guatemalan campesinos from the disputed border area and mass occupations of privately owned fincas by peasant groups. Drug traffickers have also moved into Petén to set up marijuana plantations and fly cocaine in from South America to the region's remote airstrips.

The hub of the department is Lago de Petén Itzá, where the three adjacent lakeside towns of Flores, Santa Elena and San Benito together form the only settlement of any size. You'll probably arrive here, if only to head straight out to the ruins of Tikal, Petén's prime attraction. Arriving from Belize it's probably better to base yourself at the small village of El Remate, halfway between Flores and Tikal. If you plan to reach any of the more distant ruins – El Mirador, Nakbé or Waka' – then Flores is again a good base for planning an expedition, while the fascinating site of Yaxhá is now much more accessible and attracting increasing numbers of visitors. To the south is Sayaxché, surrounded by yet more Maya sites, such as Ceibal, with its finely preserved carvings, and the ruined cities of the Lago de Petexbatún region, including the impressive Aguateca. From Sayaxché you can easily reach the ruins of Yaxchilán in Mexico, or take an alternative route back to Guatemala City – via Cobán in Alta Verapaz.