The Istra rises near the urban-type settlement Powarowo northwest of Moscow, such as between cities and Zelenograd Solnechnogorsk. Shortly after the source goes on in the 1935 Istra formed, 22 kilometers long and up to three kilometer wide Istra Reservoir, which serves as one of the reservoirs for water supply of Moscow. Just south of the dam, the river passes named after him the same city (formerly called Woskressensk ), crosses the main railway highway Moscow -Riga and flows on curvy in the southeastern direction. In the village of Petrowo - Dalneje, just south of the cities and Krasnogorsk Dedovsk, opens the Istra in the Moscow River. In the lower reaches and estuary area of the Istra reaches a width of about 20 to 30 meters. The river is fed mainly by meltwater.
Except for the city of Istra there are no major towns on the river bank. Because of this, as well as the continuously forested landscape in the river, the banks of the Istra and the reservoir are considered popular recreation area in the Moscow metropolitan area. In the 19th century inspired the nature of the Istra landscape painter Levitan, at the Woskressensk had a summer home. In Soviet times, emerged on the banks of Istra numerous sanatoriums and hostels.
The pilgrimage known as New Jerusalem Monastery, located on a high bank section of Istra, the river owes its nickname "Russian Jordan".