Oka River, a river in western Russia. It is 940 miles (1,513 km) long. From its source in the Central Russian Uplands, the river flows generally northward to Nizhniy Novgorod, where it joins the Volga River.
WHAT'S INSIDE: PHYSICAL FEATURES
Central Asia, an indefinite region in the interior of Asia. It is generally considered to extend in a broad band from the Caspian Sea into the Xinjiang region of China, covering roughly the same area as Turkestan.
Tonle Sap, a lake in central Cambodia, drained by the Tonle Sap River. During the rainy season the lake receives water from many streams, mainly the flooding Mekong River, and greatly increases in size, inundating surrounding areas.