Balaton (băˈlətŏn, Hung. bŏˈlŏtôn) [key], lake, 230 sq mi (596 sq km), W central Hungary, at the foot of the Bakony Forest. The Zala River is its main tributary; the lake is drained by the Sió River. It is the largest lake in Central Europe with many tourist and health resorts. Its shallow waters abound in fish, and along the shores are fine vineyards. Overdevelopment and poor environmental management have raised concerns about the "health" of the lake.