This ancient structure, surrounded by a nice little park, is located near the western end of the city of Milas (ancient Mylasa) in southwestern Turkey. I photographed it last July when I walked past it. Unfortunately, I didn’t have time to examine it more closely.
It is known by its Turkish name Gümüşkesen (ş=sh), which means "silver cutter". How it acquired that name, I have no idea.
Although apparently there isn't much known about it, it is considered a significant monument, because it is believed to have been modeled after the Mausoleum that once stood in Halicarnassus1, 2. Jeppesen2 calls it a Roman tomb and according to Akurgal1 it is probably from the 2nd century A.D. Bean3 gives some structural information and indicates that the door in the front provided access to the grave-chamber.
It is not known who was buried in it.
1. Akurgal, E. 1973. Ancient Civilizations and Ruins of Turkey.
2. Jeppesen, K. undated. The Maussolleion at Ancient Halicarnassus. [Booklet purchased at the Mausoleum in Bodrum, August 2002.]
3. Bean, G. 1971. Turkey Beyond the Maeander.