Sapanca Lake is a freshwater lake of tectonic origin. It is situated in the cities of Sakarya and Kocaeli. Both the lake and the districts around it—Arifiye, Sapanca, Serdivan, and Kartepe—are also visited sites. Kartepe is especially a preferred destination for winter sports. The lake and the region are popular destinations for day trips and weekend vacations for both summer and winter.