This chapter focuses on the function of E Groups, proposed as astronomical observatories by researchers at Uaxactún. Other functional hypotheses suggested include the scheduling of agricultural or trade activities, marking solar cycles and celebratory katun endings, use in geomantic systems by the Maya, use as settings for agricultural ritual, and for ancestor rituals and dynastic interment by the ruling elite. These types of architectural assemblages in the Belize Valley often contain three structures in a linear, north to south, arrangement on the east side of a large public plaza with a pyramidal structure or a range-type building on the western side. The evidence in this region suggests that these architectural assemblages were primarily used for ancestor related rituals and that classifying them as Eastern Triadic Assemblages may be appropriate in order to distinguish them from E Groups like the one at Uaxactún.