Karaca Hisar or Karacahisar Castle is located in the southwest of Eskişehir and covers a walled area of about 200 x 300 meters on a plateau at an altitude of 1010 meters above sea level. From some important data, there are still doubts about the period in which the castle was built and named, but it is known that it was one of the important castles in the line of defense of the region during the Byzantine period.