The classic Maya culture started to decline in the 8th and 9th centuries A.D. Most of the cities of the central lowlands had been abandoned. Earthquakes, invasions by outsiders, famine, warfare, and drought have all been suggested as possible causes for the fall of the Mayan civilization. By 900 A.D. almost all of the ceremonial centers had been abandoned. Jungle growth had hid many of the sites from destruction by the Spanish conquistadors. The Spanish started to conquer the Maya lands from 1520 to 1697. Still, some of the Maya's numerous ceremonial sites avoided destruction. They remained hidden and somewhat preserved in the jungle until around the 19th century.
Study of these areas takes such a long time because of the hot and rainy climate. When it rains, the studies stop. The thick rainforests also make it impossible for the archeologists to search the areas by helicopter; therefore to study it, the people have to go out on foot through the jungle.
Although the popular myths say that the Maya people disappeared, that is not true. Many Maya people still live in those regions today. They even still speak one of the many Maya languages.