The Belen mosque, where the brick and stone materials on its walls belong to the ancient period, survives from the 14th century to the present day. The historical mosque is located on Hisarbaşı Hill within the borders of Mugla Milas. Since it does not have an inscription, It is not possible to talk about the exact date of construction of the mosque. The same ambiguity applies to the constructive of the mosque.
The Belen mosque was originally built as a church but converted into a mosque by a person named Hodja Mukbil. The mosque is more like the Grand Mosque with its general lines and architectural features. The ceiling section of the structure is seen to be wooden. The masonry areas are a mixture of stone and brick. The exterior is left without plaster.
The first serious repair of the Belen mosque took place in 1750. This repair was made by Mehmet Sait Agha at that time. The places of worship are separated by three columns. These columns are connected to each other by means of sharpish arches. Wooden ceilings stand out over each section where worship is performed. The entrance gate of the mosque is in the northern part. On the other hand, there is a small entrance door in the western part. Next to the mosque, the minaret with one balcony, which was laid on cut stone, was later incorporated. This round-bodied minaret was built by Ömer Agha. The dome part of the mosque has a polygonal pulley structure.
Due to the increasing population in Belen, an additional building is constructed to the historic mosque. This building is located just east of the mosque. It is possible to enter this section from Harim(sanctuary). The additional area, including the mihrab, is simply designed. In 2010, the Regional Directorate of Foundations decided to restore the courtyard of the mosque in its original form. The Belen mosque is still open for worship today. The mosque is located on the road referred as’ Yukarı Çarşı (Upper Bazaar)'. In a sense, it is in the center of the bazaar.