The Lost World Pyramid began as a small astronomical viewing platform which faced three structures to its east which marked, in turn, the position of the rising sun at the spring solstice (north building), the equinox (center building), and the winter solstice (south building).
"The location of the Lost World Pyramid was first occupied in the earliest times of Tikal's settlement. A pyramid with four stairs, one to each side, is called a radial pyramid, and the first version was built by 500 BC. The astronomical concept was formalized with new constructions between 500 and 250 BC in the Late Preclassic including a new radial platform and a new eastern platform, both much larger than the prototype from the Middle Preclassic. The importance of the east-west axis was established at this time by the placing of burials and caches along it. There is a contrast between this formal and ritual complex with that of the other major contemporary complex, the North Acropolis in which the ritual axis of importance to burials was north-south."
Peter Harrison, The Lords of Tikal, p. 56