The riverboat season is winding down, but there is still time to hop aboard and enjoy the last of the summer by sailing through the Russian heartland. Cruises last from three days to a week, or more, taking passengers from Moscow to points north and south. The boats dock at towns along the way and offer tours of historic sights. They also drop anchor at so-called green stops, where passengers can walk in the woods or swim. Prices vary greatly, depending on the type of accommodations. At the top end of the scale are air-conditioned staterooms with private showers and toilets. For much less money, passengers can book a bunk in a cabin without bathroom facilities, although most have a basin with hot and cold running water. Stolichnaya Sudokhodnaya Kompaniya, or Capital Shipping Company, is the main boat operator and offers numerous cruises. The cruises are round-trip unless otherwise noted, and prices include three meals a day. The company is located at North River Port, 51 Leningradskoye Shosse, Tel.