Eastern Naxos, near village of Danakos. Fotodoti Monasteri built in the the IX century on the ruins of the sixth century Christian basilica.
Sources:
George Dimitrokallis, “The Byzantine Churches of Naxos.” American Journal of Archaeology, vol. 72, no. 3, Archaeological Institute of America, 1968, pp. 283–86, https://doi.org/10.2307/503558.