The length of the Saidė stream is only 5 km, and only the lowland of the stream belongs to the Neris Regional Park. The Saidė outflows from Didžiulis Lake. The water surplus of the great Trakai lakes flows with this stream and with the Bražuolė to the Neris. The stream is refreshed by the springs gushing out of its steep slopes. With a view to preserving the unique torrential Saidė stream, the boulders in its riverbed, the narrow steep-sloped canyon and the confluence with the Neris, the Saidė hydrographical strict nature reserve has been established.