Half the fun in San Francisco takes place outdoors. If you're not in the mood to trek it, there are other things to do that allow you to enjoy the surroundings.

Ballooning -- Although you must drive 1 hour to get to the tour site, hot-air ballooning is an ethereal and silent flight over the Wine Country. Adventures Aloft, P.O. Box 2500, Vintage 1870, Yountville, CA 94599 (tel. 800/944-4408 or 707/944-4408; www.nvaloft.com), is Napa Valley's oldest hot-air balloon company, staffed with full-time professional pilots. Groups are small, and each flight lasts about an hour. The cost of $195 per person ($160 ages 6-16) includes a post-adventure champagne brunch and a framed "first-flight" certificate. Flights launch daily from 6 to 7am (weather permitting).

Biking -- The San Francisco Parks and Recreation Department maintains two city-designated bike routes. One winds 7 1/2 miles through Golden Gate Park to Lake Merced; the other traverses the city, starting in the south, and continues over the Golden Gate Bridge. These routes are not dedicated to bicyclists, who must exercise caution to avoid crashing into pedestrians. Helmets are recommended for adults and required by law for kids under 18. A bike map is available from the San Francisco Visitor Information Center, at Powell and Mason streets (see "Visitor Information" in chapter 4), and from bicycle shops all around town.

Ocean Beach has a public walk- and bikeway that stretches along 5 waterfront blocks of the Great Highway between Noriega and Santiago streets. It's an easy ride from Cliff House or Golden Gate Park.

Avenue Cyclery, 756 Stanyan St., at Waller Street (tel. 415/387-3155), rents bikes for $5 per hour or $25 per day. It's open daily, April through September from 10am to 7pm and October through March from 10am to 6pm.

Boating -- At the Golden Gate Park Boat House (tel. 415/752-0347) on Stow Lake, the park's largest body of water, you can rent a rowboat or pedal boat by the hour and steer over to Strawberry Hill, a large, round island in the middle of the lake, for lunch. There's usually a line on weekends. The boathouse is open daily from 10am to 4pm, weather permitting.

Cass Marina, 1702 Bridgeway, Sausalito (tel. 800/472-4595 or 415/332-6789; www.cassmarina.com), is a certified sailing school that rents sailboats measuring 22 to 101 feet. Sail to the Golden Gate Bridge on your own or with a licensed skipper. In addition, large sailing yachts leave from San Francisco and Sausalito on a regularly scheduled basis. Call or check the website for schedules, prices, and availability of sailboats. The marina is open daily from 9am to sunset.

City Stair Climbing -- Many health clubs have stair-climbing machines and step classes, but in San Francisco, you need only go outside. The following city stair climbs will give you not only a good workout, but great sightseeing, too.

Filbert Street Steps, between Sansome Street and Telegraph Hill, are a particular challenge. Scaling the sheer eastern face of Telegraph Hill, this 377-step climb winds through verdant flower gardens and charming 19th-century cottages. Napier Lane, a narrow, wooden plank walkway, leads to Montgomery Street. Turn right and follow the path to the end of the cul-de-sac, where another stairway continues to Telegraph's panoramic summit.

The Lyon Street Steps, between Green Street and Broadway, were built in 1916. This historic stairway street contains four steep sets of stairs totaling 288 steps. Begin at Green Street and climb all the way up, past manicured hedges and flower gardens, to an iron gate that opens into the Presidio. A block east, on Baker Street, another set of 369 steps descends to Green Street.

Fishing -- Berkeley Marina Sports Center, 225 University Ave., Berkeley (tel. 510/849-2727), makes daily trips for ling cod, rock fish, and many other types of game fish year-round, and it makes trips for salmon runs April through October. Fishing equipment is available; the cost, including boat ride and bait, is $65 per person, $70 during winter when it's a crab-and-fish combo. Reservations are required, as are licenses for adults. One-day licenses can be purchased before departure. Find out the latest on the season by contacting their hot line at tel. 510/486-8300. Excursions run daily from 6am to 4pm. Fish are cleaned, filleted, and bagged on the return trip for a small fee.

Handball -- The city's best handball courts are in Golden Gate Park, opposite Seventh Avenue, south of Middle Drive East. Courts are available free, on a first-come, first-served basis.

Running -- The Bay to Breakers Foot Race (tel. 415/359-2800; www.baytobreakers.com) is an annual 7 1/2-mile run from downtown to Ocean Beach. About 80,000 entrants take part in one of San Francisco's trademark events. Costumed participants and hordes of spectators add to the fun. The event, sponsored by the San Francisco Examiner, is held on the third Sunday of May.

The San Francisco Chronicle Marathon takes place annually in the middle of July. For more information, call tel. 415/284-9653 or visit www.chroniclemarathon.com.

Great jogging paths include the entire expanse of Golden Gate Park, the shoreline along the Marina, and the Embarcadero.

Skating (Conventional & In-Line) -- Although people skate in Golden Gate Park all week long, Sunday is best because that's when John F. Kennedy Drive between Kezar Drive and Transverse Road is closed to automobiles. A smooth "skate pad" is on your right, just past the Conservatory. Another hot skating, biking, and walking spot is the newly renovated Embarcadero Promenade, which stretches from the new Pacific Bell Park (Townsend St. and Embarcadero) to Fisherman's Wharf. Skates on Haight, 1818 Haight St. (tel. 415/752-8376), 1 block from the park, is the best place to rent in-line or conventional skates. The cost of $6 per hour, $24 per day, includes protective wrist guards and kneepads. A major credit card and ID deposit are required. The shop is open Tuesday through Friday from 11am to 7pm, Saturday and Sunday from 10am to 6pm.

Tennis -- The San Francisco Parks and Recreation Department (tel. 415/753-7001) maintains more than 100 courts throughout the city. Almost all are available free, on a first-come, first-served basis. The exceptions are the 21 courts in Golden Gate Park, which cost $4 to $6. Courts must be reserved for weekend play by calling tel. 415/753-7101 on Wednesday from 4 to 6pm, Thursday from 9am to 5pm, or Friday from 9am to noon. For midweek reservations, call tel. 415/753-7001.

Walking & Hiking -- The Golden Gate National Recreation Area offers plenty of opportunities. One incredible walk (or bike ride) is along the Golden Gate Promenade, from Aquatic Park to the Golden Gate Bridge. The 3 1/2-mile paved trail heads along the northern edge of the Presidio out to Fort Point, passing the marina, Crissy Fields' new restored wetlands, a small beach, and plenty of athletic locals. You can also hike the Coastal Trail all the way from the Fort Point area to Cliff House. The park service maintains several other trails in the city. For more information or to pick up a map of the Golden Gate National Recreation Area, stop by the park service headquarters at Fort Mason at the north end of Laguna Street (tel. 415/561-4700).

Although most people drive to this spectacular vantage point, a more rejuvenating way to experience Twin Peaks is to walk up from the back roads of U.C. Medical Center (off Parnassus) or from either of the two roads that lead to the top (off Woodside or Clarendon aves.). The best time to trek is early morning, when the city is quiet, the air is crisp, and sightseers haven't crowded the parking lot. Keep an eye out for cars, however, because there's no real hiking trail, and be sure to walk beyond the lot and up to the highest vantage point.