Another relevant archaeological zone of El Salvador in addition to Chalchuapa, is the Valley of Zapotitán, whose main center was the archaeological site of San Andrés, located near the Río Sucio (Dirty river). Although there is evidence of their occupation from the Pre-classic period, its main buildings date from the late classic period, after the eruption of the 536 B.C. corresponding to the eruption of the Llopango. The majority of buildings were built with bricks of adobe as core covered by layers of mortar known in Spanish as “repellos de argamasa”. San Andrés has an Acropolis and La Gran Plaza is located to the North. The Acropolis has in its interior structure 1, a pyramidal structure of 15 m in height, where at least you can see 4 constructive stages. Other three small pyramids (2, 3, and 4 structures) are located in row on the East side of the Acropolis. The rest of the complex was shut down on the West side by a row of quarter-perishable architecture, known as “Los Apartamentos”. 5 structure or the campaign the pyramid is the largest of the site building and delimits the Gran Plaza at its northeastern end. Southeast of the Acropolis lies structure 7, which is the only one that presents masonry of blocks of Tuff, inside of which was found an offering with polychrome vessels, an offering of eccentric Flint, and other imported objects, indicating strong relationships with Copán and the Maya lowlands.