Pyramid C1 is the principal structure in Group C. Archaeological investigation uncovered three versions of the pyramid, each built over the last. The archaeologists restored the pyramid in such a way as to make a part of each of the three construction phases visible. The first phase of construction consisted of a platform of cut pumice blocks. This was buried under the second construction phase, which consisted of a five-level stepped pyramid. It had a double stairway on the west side; each stairway had 16 steps. The stairways were flanked and separated by ramps that terminated in sizeable masonry blocks at the top. The top of the pyramid stood high and was topped by a temple, parts of which survive and have been restored. The walls were built from packed earth coated with stucco; a section of the northern portion of the rear wall still stands to a height of . A wide stucco bench was built against the rear wall and a concave hollow in the floor was probably designed for the burning of incense. The roof of the temple was likely to have been thatched. The third and final construction phase was considerably larger than the preceding versions of the pyramid. In its final form the pyramid base measured ; it had five corniced levels and only possessed a single stairway in place of the earlier two.The stairway was flanked by two wide ramps, only the lower portion of the stairway and ramps survive. The top of the pyramid stood almost higher than the preceding version and preserved parts of the earlier temple building in its infill; the upper platform has largely collapsed and no trace remains of the final version of the temple superstructure. Both the second and third versions of the pyramid were originally coated in stucco, parts of which were preserved. New stucco was applied during restoration work to match the original coating. Although the pyramid was restored after it was excavated, the 1976 Guatemala earthquake caused considerable damage and the upper portion of the pyramid was reduced to rubble.