Several organizations conduct tours of the mansions and the downtown historic district. Between May 15 and October 15, the Newport Historical Society, 82 Touro St. (tel. 401/846-0813), offers a few different itineraries of considerable variety and length. Tickets cost as little as $4 and as much as $12. They can be purchased at the Society or at the Gateway Visitor Center.

Viking Tours, based at the Gateway Visitor Center, 23 America's Cup Ave. (tel. 401/847-6921), has narrated bus tours of the mansions and harbor cruises on the excursion boat Viking Queen. Bus tours -- daily in summer, Saturdays from November to March -- are 1 1/2 to 4 hours and cost $22 to $47 for adults, $13 to $21 for children 5 to 11. Boat tours, from late May to early October, are 1 hour in length and cost $12 for adults, $10 for seniors, and $6 for kids. In July and August, the cruise can be extended to include a stop and tour of Fort Adams; $17 for adults, $15 for seniors, and $9 for children.

Classic Cruises of Newport, Bannister's Wharf, schedules narrated cruises on its 72-foot schooner Madeleine (tel. 401/847-0298). There are daily departures from spring to late fall; fares are $25 or $30 (children under 12 $5 off). The company's classic powerboat RumRunner II (tel. 401/847-0299; same website) offers cruises daily over the same period. Rates are $17 per person for most outings, $22 for the cocktail cruise.

The Spirit of Newport, 2 Bowen's Wharf (tel. 401/849-3575), offers daily 1 1/2-hour cruises of the bay and harbor from May 1 to Columbus Day; Fares are $13 for adults, $11 for seniors, $7 for children ages 4 to 12. Another possibility is the Adirondack , a 78-foot schooner that makes 2-hour cruises from the Newport Yachting Center (tel. 401/846-3018). Its ticket booth is on America's Cup Avenue at Commercial Wharf; reservations must be made in advance. Daily departures cost $25 to $30, depending on the time of day.

The Newport Touring Company, 19 America's Cup Ave. (tel. 800/398-7427 or 401/841-8700), features 90-minute round-trip excursions in vintage railroad trains along the edge of the bay. Fares are $15 for adults; kids 10 and under are free, but only one per paying adult; additional kids are charged $7.95. The company also has a dinner train that operates Thursdays through Saturdays, mid-April to mid-December. Variations include a rail-and-cruise luncheon, and cabaret and murder mystery dinners, with prices per person from $43 to $54.