Pyramid E1 is located on the east side of the Group E plaza and was the most important building in Group E. The pyramid had three construction phases, the oldest of which was built from pumice upon a natural high elevation and was found to be well preserved during excavations of the site. This early phase was packed with rounded pebbles to provide the infill for the second phase of construction. The second version of the pyramid was very poorly preserved; excavations uncovered many stucco fragments but were unable to determine which of the first two construction phases they belonged to. The third and final phase of construction was larger than the preceding versions of the building and encased both them and the natural elevation upon which they stood. The pyramid had four stepped levels upon a basal platform. It faced west with an access stairway flanked by two ramps that terminated in projecting masonry blocks at the top. A small altar was excavated at the base of the pyramid; two stones were found placed upon it. One of these stones was ball-shaped while the other was perforated and may have been a mace or club. A number of funerary urns were excavated at the base of the southern side of the pyramid.