The monastery sits on Siniyah Island, which shields the Khor al-Beida marshlands in Umm al-Quwain, an emirate some 50 kilometers (30 miles) northeast of Dubai along the coast of the Persian Gulf. The island, whose name means “flashing lights” likely due to the effect of the white-hot sun overhead, has a series of sandbars coming off of it like crooked fingers. On one, to the island’s northeast, archaeologists discovered the monastery. Carbon dating of samples found in the monastery’s foundation date between 534 and 656. Islam’s Prophet Muhammad was born around 570 and died in 632 after conquering Mecca in...