The Lost World Pyramid ( Structure 5C @-@ 54 ) is the largest structure in the Mundo Perdido complex . It lies in the southwest portion of Tikal ’ s central core , south of Temple III and west of Temple V. It was decorated with stucco masks of the sun god and dates to the Late Preclassic ; this pyramid is part of an enclosed complex of structures that remained intact and un @-@ impacted by later building activity at Tikal . By the end of the Late Preclassic this pyramid was one of the largest structures in the Maya region . It attained its final form during the reign of Chak Tok Ich 'aak in the 4th century AD , in the Early Classic , standing more than 30 metres ( 98 ft ) high with stairways on all four sides and a flat top that possibly supported a superstructure built from perishable materials . Although the plaza later suffered significant alteration , the organization of a group of temples on the east side of this complex adheres to the layout that defines the so @-@ called E @-@ Groups , identified as solar observatories .