Puerto Quetzal, on the Pacific coast of Guatemala, gives access to Guatemala City, the capital, beaches and some significant historical sites. Magnificent buildings of the colonial period remain at Antigua, the colonial capital, located near Guatemala City. Guatemala was the center of the old Mayan civilization, and many sites from the classic Mayan period (3rd-10th century AD) have been excavated and studied. The largest of these is Tikal in the northern lowlands, where some 3,000 structures, including tall temple pyramids as well as plazas and monuments, cover an area of about 6 sq miles. Thought to have sustained a population of 50,000 at its peak, it was abandoned for unknown reasons at the end of the 10th century.