The summit shrine was accessed via a 16.3-metre (53 ft) wide stairway that climbed from the supporting platform; a plain stela (Stela 43) and the associated Altar 35 are centrally located at the base of the stairway.[6] The shrine has been partially restored and has walls up to 12 metres (39 ft) thick. The shrine was built upon a platform resting upon a supplementary platform, which was in turn seated upon the top of the pyramid