Group E Observatory Complex

17.3958°N, 89.6339°W.

The Group E Observatory Complex at Uaxactún in the Petén Basin of northern Guatemala is the type-site for the "E-Group" — an architectural arrangement found at over 80 Maya sites and designed for solar horizon observation. The complex consists of a western pyramid (Structure E-VII-sub) facing east toward a long platform supporting three small temples. From the western pyramid's summit, the rising sun aligns with the centre temple at the equinoxes, the southern temple at the winter solstice, and the northern temple at the summer solstice. The complex was built up between approximately 600 BCE and 300 CE during the Late Preclassic and modified through the Early Classic. Frans Blom of Tulane University identified the alignment in 1924. Structure E-VII-sub itself, beneath the later phases, is a Late Preclassic pyramid faced with sixteen large stucco masks.

Group E is a building configuration that turned the eastern horizon into an annual calendar.