Karacahisar castle

Karacahisar Castle (sometimes spelled as Karajahisar Castle) is a Byzantine castle built on a plateau. It is near the Porsuk River, southwest of Eskişehir, Turkey. Karacahisar Castle stands above sea level. It is surrounded with walls and covers an area of 60,000 square meters. 
The Turks settled in the region and called it Karajshahir. In 1299 Osman I appointed judge and imam . After possessing the Karacahisar castle, Osman advanced on the Byzantine lands and expanded the borders of the emirate. The conquest of Karacahisar was important in laying the foundation for the Ottoman Empire.