Kışlaçay is a neighborhood in Geyve District, in Sakarya Province, Türkiye. Kışlaçay lies at 138 m above sea level, in the Köroğlu mountains. It has 330 inhabitants. The nearest city is Sapanca, 11.0 km to the west. Among the landmarks around are Sangarius Bridge (10.3 km), Nicomedia (42 km) and Sakarya Museum (14.4 km). Among the natural features are Doğançay Waterfall (5.1 km).