The foundations are made of gray kara limestone, but yellow poros and limestone from the Acropolis were also used in the walls. Because of the steepness of the slope, the south end of the temple sits directly on the bedrock, while the north end required ten courses of masonry. The cuttings in the bedrock for the temple's foundations are still visible on the western side. The foundations were built of high-quality polygonal masonry, without clamps or dowels. The foundation blocks survive for the whole north side and parts of the western and eastern sides. The foundations of the cross-wall that separated the pronaos from the cella are partially preserved. An extension was added to the east side of the temple during construction, which measures 2.20-2.355 m wide and is composed of red crystalline blocks originally cut for use in some other context. The addition may have been made so that the width:length ratio of the temple would be closer to the golden ratio, which became popular in temple construction at this time.
The foundations are made of gray kara limestone, but yellow poros and limestone from the Acropolis were also used in the walls. Because of the steepness of the slope, the south end of the temple sits directly on the bedrock, while the north end required ten courses of masonry. The cuttings in the bedrock for the temple's foundations are still visible on the western side. The foundations were built of high-quality polygonal masonry without clamps or dowels. The foundation blocks survive for the whole north side and parts of the western and eastern sides. The foundations of the cross-wall that separated the pronaos from the cella are partially preserved. An extension was added to the east side of the temple during construction, which measures 2.20-2.355 m wide and is composed of red crystalline blocks originally cut for use in some other context. The addition may have been made so that the width:length ratio of the temple would be closer to the golden ratio, which became popular in temple construction at this time.