During the Maya Classic period, 250 - 900 AD, the Cayo area was heavily populated - archeologists estimate Caracol alone had over 100,000 people. By 1200 AD, the Mayan city-states and towns were deserted. Tropical jungle grew over everything, and the great stone pyramids and palaces were hidden. In the 20th century, the ruins were discovered, and now kids can climb up Maya temples, where once only royalty sat at the top.