Recent investigations at the Maya centre of Nakum (in Guatemala) enabled the study of the evolution of an interesting complex of buildings that started as the so-called E-Group, built during the Preclassic period (c. 600-300 BC). It was used for solar observations and rituals commemorating agricultural and calendrical cycles. During the Classic period (AD 250-800), the major building of the complex (Structure X) was converted into a large pyramidal temple where several burials, including at least one royal tomb, were placed. We were also able to document evidence of mortuary cults conducted by the Maya in the temple building situated above the burials. The architectural conversion documented in Structure X may reflect important religious and social changes: a transformation from the place where the Sun was observed and worshipped to the place where deceased and deified kings were apotheo-sized as the Sun Deity during the Classic. Thus the Maya transformed Structure X into one of the most sacred loci at Nakum by imbuing it with a complex solar and underworld symbolism and associating it with the cult of deified ancestors.