Gelioniai Hill is located in Prienai district, in Stakliškės municipality. It is one of the highest hills of the Mergiškiai Landscape Reserve, separating the villages of Antaveršis and Polesė. The hill consists of glacier streaks containing 30-40% of the gravel that is of 2-80 mm in diameter. Next to it lies Lake Gelioniai, the highest in the regional park. In the Soviet years, the hill was excavated for high-quality aggregate building materials. There is a viewing site (lookout) on this hill, from which the panorama of Lake Antaveršiai and the village of Užuguostis open. Next to it is Radio Station I of the Air space observationa and control board of the Lithuanian Armed Forces.