At the peak of the great Maya civilization, around AD 800, the density of its cities exceeded 2,000 people per square mile, similar to Los Angeles County today. By AD 950, however, populations had declined as much as 95 percent. The collapse remains a dark mystery. Why did they stop building their splendid cities? Where did they all go?

Although the cities died, the people endured. Distinctive Maya faces still appear through­out Central America. They seem familiar from the friezes on ancient temples and pictures in history books.

Early explorers mapped Belize unaware of the vast cities hiding just under their feet. Thousands of structures - some still taller than modern Belizean buildings - waited patiently in the jungle. Excavated in the 20th century, they now testify about the ancient Maya civilization, which endured longer than the Roman Empire.

Majestic temples offer clues, but archaeologists still debate whether the civilization collapsed due to drought, war, disease, or political instability. Perhaps all were mere symptoms. Current theory points to a food and water shortage, caused by natural drought and deforestation by the Maya themselves. Evidence shows that deforestation coincided with malnutrition and the drop in population.

The Maya began to build magnificent cities and ceremonial centers more than 2,000 years ago. Observing movements of the sun, moon, and planets, they developed complex calendars, with cycles for agriculture, religion, and politics. They invented the concept of zero, which led to major advances in math and science.

The Maya also made war, practiced bloodletting, and sacrificed each other. They believed such religious and cultural imperatives sustained the gods and insured abundant agriculture.

Excavations at Altun Ha, Lamanai, and Xunantunich, in the 1960s and 1970s, first revealed the profundity of Belizean heritage. In 1986 researchers discovered glyphs at Caracol celebrating the city's military victory over mighty Tikal, in present-day Guatemala. Now scholars understand that some Belizean cities reigned over others, and that Belize stood at the very center of the Maya world.

Sites throughout the region remain unexplored, waiting for the living to decipher the secrets of the dead. The enigmatic civilization gives up these secrets slowly, as lexicographers work to decode Mayan hieroglyphics carved into stones called stelae. Each stela records a sensational story of war, peace, and the exploits of a powerful ruler.

One of only five complete writing systems developed in history, the Maya's ingenious hieroglyphics employ complex interchangeable glyphs that represent whole words or phonetic sounds and appear as artistic calligraphy. Preserved in sculpted stone and painted ceramics, Mayan hieroglyphics record calendrical, astronomical, religious, and historical data. It took 100 years to crack the code, but today scholars know the names of many rulers and the dates of their achievements.

In the Postclassic period, AD 1000-1540, locals plied a trade route stretching from current-day Mexico to Panama. Artifacts found at various sites indicate the Maya maintained business and cultural connections with faraway places, including the Teotihuacan metropolis in Mexico.

Some Belizean sites - Xunantunich, el Pilar, la Milpa, Cahal Pech, Santa Rita, and Lamanai - were regional centers, and the super regional center of Caracol rivaled leading cities in Mexico and Guatemala. Altun Ha and Lubaantun served as trading centers between the Caribbean and the interior. In the Preclassic period, Cerros was a port of entry for Lamanai. Small southern sites - Nim Li Punit, Uxbenka, and Pusilha - orbited the great Copan in Honduras and Quirigua in Guatemala.

Choosing which sites to visit depends on time and interest. Xunantunich, visually im­pressive and easy to reach, has a crenellated top and magnificent frieze. Lamanai features a pyramid dating to the time of Christ, and sits at the end of a cool 90-minute New River cruise. Altun Ha, close to Belize City, looks like a well-manicured park. Caracol features three temples rising 145 feet above the jungle floor.

Up north, Cerros perches on white-capped Corozal Bay. Down south, the builders of Lubaantun fitted stones entirely without mortar. At Nim Li Punit, one carved monument stands three stories tall. At el Pilar, a site shared between Belize and Guatemala, a hundred acres of unrestored structures remain hidden, and a dozen large pyramids and residential structures await excavation.

To get the most from a site, hire a certified tour guide, found in the Belize Tourism Industry Association directory in this book, or through the Belize Tourism Board at 223-1910/13. Wear lightweight cotton clothing, shoes with good tread, and long pants. Bring sunscreen, insect repellent, bottled water, snacks, hat, and camera with extra film or batteries. Major Maya sites are listed with other tours and attractions in the previous story.