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Structure VI and its companion across the plaza, Structure IV, form a kind of celestial observatory called an "E Group." An E Group is composed of an observation platform on the west facing a group of three sighting temples to the east. The eastern temples mark the positions of the rising sun at the summer solstice (north temple), the winter solstice (south temple), and the equinox (central temple).
This configuration gets it name from the E-7-Sub group of structures at Uaxactun, where this type of complex was first identified. Another famous example of an E Group is the Lost World pyramid complex at Tikal.