The island, which is in the south of Fethiye, is approximately 9 kilometers from Fethiye. The island is 1 km long and 400 meters wide. The southern slope of Gemiler Island is steep and the northern slope has a slight inclination. In the Middle Ages, Gemiler or Aya Nikola Island, which is located in the Ölüdeniz Basin known as Smybola, came to an important position with the formation of religious settlements from the 5th century AD. There are some rumors about the name of the island. For example; It was found in a medieval maritime guide that the church at the highest point of the island was dedicated to St. Nicholas. However, the accuracy or rejection of some of the information that this St. Nicholas is thought to have been born in Demre and known as Santa Claus is still uncertain. An important Nicholas lived on this island, but there is no detailed information about her identity yet.
The Japanese archeology team conducted a survey on the island in 1990. Between 1995 and 2003, archaeological excavations were carried out together with the Fethiye Museum Directorate and the Japanese University of Osaka.
In the investigations carried out in Gemiler Island, Karacaören Island and its vicinity, 11 Basilica type churches, as well as many chapels, houses, warehouses, tombs and cisterns were found. Religious buildings, in which cut stones are partially used, were mostly built with local stones and very little bricks were used. On the island, where there are frescoes for religious purposes on the walls of the churches, the floors of the churches covered with mosaic have been destroyed. On the hill, there is a 2.5 meter wide and 160 meter long vaulted road between the two churches named as number 2 and 3 on the east - west ends.
With a wall extending in the east-west direction on the northern slope of the island, the religious buildings concentrated on the upper part of the hill and the civil and commercial buildings below can be distinguished from each other. This situation indicates that the upper part of the island is a sanctuary.
It is thought that the presence of a chimney, which is thought to be used to give a signal with smoke, on the Karacaören Island, approximately 150 meters west of the island, is thought to be intended to warn both the people of Gemile Island and the people of Kayaköy against the danger in case of a possible attack.
Gemile Island being the center, Gemile Bay, Ölüdeniz, Fethiye Peninsula, Knight Island and the bay where 12 islands are located, there are many churches and chapels scattered in various notes and this gives the impression that there was an intense religious activity during the period of the region.
The fact that there are so many religious buildings in and around Gemile Island, which is understood to have been settled between the 5th and 13th centuries AD, may be related to the increase of pilgrimages by sea from Asia Minor to the Aegean and Mediterranean coasts in the 5th and 7th century. It also reveals the relationship of the ancient age and Byzantium with the Near East and Europe in terms of maritime trade.
In the Middle Ages, apart from religious buildings, there are also houses for living and working people. Because the island is rocky, the foundations of churches and houses are carved into the rock. The ruins can also be seen on the sea surface.