The Temple Apollo at Halasarna existed in Archaic Period. Its foundations have been uncovered underneath a building of the early Christian period.
See:
- G.Kokkorou-Alevras, D. Grigoropoulos, C. Diamanti and M. Koutsoumpou: Maritime Connections of Halasarna on Cos from Prehistory to Late Antiquity: A View Based on the Pottery and Other Finds, in: Ancient Ports. The Geography of Connections Proceedings of an International Conference at the Department of Archaeology and Ancient History, Uppsala University, 23–25 September 2010, BOREAS: Uppsala Studies in Ancient Mediterranean and Near Eastern Civilizations (Book 34), Uppsala Universitet; Illustrated edition, 2016, pp. 167-200
- https://www.discoveringkos.com/destination-item/alasarna/