The large prehistoric mound of Küllüoba is an irregular oval some 300 x 150 m, rising nearly ten meters above the plain level in the rolling cultivated fields of the upper Sakarya (Sangarius) basin just north of the Phrygian Highlands: 35 km SE of Eskişehir, 15 km NE of Seyitgazi and 1.3 km south of the village of Yenikent.
The mound itself—on the northern slope of an ancient stream bed, now dry—is comprised almost exclusively of prehistoric deposit; our eleven excavation campaigns suggest that all phases of the Early Bronze Age are represented, underlain by Late Chalcolithic deposit. Stray finds from the Middle Chalcolithic period suggest that there are earlier strata as well. We also suspect that there is a prehistoric cemetery in the fields immediately to the NW of the mound. The latest prehistoric material on the settlement mound itself comes from the late EB III, i.e. the period transitional to the Middle Bronze Age. In the general vicinity there are also late Hellenistic remains; a Hellenistic pavement appeared above EBA deposit in the soundings in the fields SE of the citadel.
The Mound of Küllüoba is under excavation by Prof. Turan Efe from the Bilecik University, Department of Archaeology since 1996.