Platform A3 encloses the north side of the eastern part of the Group A plaza. It faces south onto the plaza and was accessed via two stairways on that side. The platform was built over an earlier structure that was built on top of an early tiered retaining wall; the earlier structure extended above the retaining wall. The final version extended further to the west and further to the north. It had two levels, each terminating in a cornice. On the north side a wide bench extends along the base of the wall.