To begin with, the ancient Greeks called it Keleris and it belonged to the “islands of Kalydna” mentioned in the “New Catalog” of the legendary author Homer, along with the rest in the region of Kalymnos. In addition, plenty of remains from the late Roman period, such as baths (hot), olive mill, are found mainly on the east coast of the island, between the large early Christian basilicas, near the present settlement. What’s more, west of the place “Tholaria” or “Pefki” with the above-ground tombs, the place of an ancient theatre is placed. Furthermore, on the imposing and steep hill of Agios Konstantinos with the fortified Byzantine settlement, located on the northern slope and around the middle of “Rachi”, at an altitude of about 120 m, there are remnants of an outpost. Remains of a Late Roman pottery workshop have been preserved at the coastal site of Vlychada. Moreover, the castle is believed to have been built in the second half of the 7th century to protect the settlement from the Arab invasions of the time and probably, after the earthquake of 535, to be abandoned. In must be noted that in the 15th century, the Florentine monk-geographer Christopher Buodelmodi visited the island, who was hosted by the Knights of St. John of Rhodes and recorded its Christian monuments.