Centre City Development Corporation's Downtown Information Center in Horton Plaza (tel. 619/235-2222; www.ccdc.com) offers free downtown bus tours the first Saturday of the month at 10am and noon. Reservations are required for the 90-minute tour, which is aimed at prospective home-buyers in the downtown area, as well as curious locals trying to stay abreast of developments. Go inside the information center to see an enormous scale model of the downtown area. The office is open Monday through Friday from 9am to 5pm.

 Tours with a Twist

If you can't decide between a bus tour or a bay cruise, opt for both -- an amphibious tour on Old Town Trolley Tour's Sea and Land Adventures. The 90-minute SEAL tour departs from Seaport Village and motors along the Embarcadero until splashing into San Diego Bay. This specially built craft holds 46 passengers, and the narrated tour gives you the maritime and military history of San Diego from the right perspective. Trips are scheduled daily April through October from 10am to 5pm, and Thursday through Monday 10am to 4pm the rest of the year. The cost is $34 for adults and $19 for kids 4 to 12. Free for children 3 and under. For information and tickets, call tel. 888/910-8687 or 619/298-8687, or visit www.historictours.com.

Another novel way to see the sights is via GoCar Tours (tel. 800/914-6227; www.gocartours.com), small, three-wheeled vehicles that zip around town at about 35 mph (56kmph). These two-person open-air minicars are equipped with GPS technology that not only gives directions, but also indicates points of interest and narrates San Diego history (in five languages). Don't feel like listening to a talking car? Just pop a disc into the CD player. GoCar Tours is at 2100 Kettner Blvd. in Little Italy and is open daily from 8:30am to 5pm. Rates start at $49 for the first hour, and you must be 18 to rent; it's suggested you reserve 24 hours in advance.

Bus Tours

Not to be confused with the public transit trolley, the narrated Old Town Trolley Tours (tel. 888/910-8687 or 619/298-8687; www.historictours.com) offer an easy way to get an overview of the city. You can tie together visits to several major attractions without driving or resorting to pricey cabs. These vehicles, gussied up like old-time trolleys, do a 30-mile circular route; you can hop off at any one of 11 stops, explore at leisure, and re-board when you please (the trolleys run every half-hour). Stops include Old Town, the Gaslamp Quarter, Coronado, the San Diego Zoo, and Balboa Park. You can begin wherever you want, but you must purchase tickets before boarding (most stops have a ticket kiosk, or you can get discounted tickets online). The tour costs $34 for adults ($17 for kids 4-12, free for children 3 and under) for one complete circuit; the route by itself takes about 2 hours. The trolleys operate daily from 9am to 5pm November to February, and 9am to 6pm March to October.

Walking Tours

Walkabout International, 2650 Truxton Rd., Ste. 110, Point Loma (tel. 619/231-7463; www.walkabout-int.org), sponsors more than 100 free walking tours every month that are led by local volunteers, listed in a monthly newsletter and on the website. Walking tours hit all parts of the county, including the Gaslamp Quarter, La Jolla, and the beaches. A wilderness hike takes place most Wednesdays and Saturdays.

Urban Safaris (tel. 619/944-9255; www.walkingtoursofsandiego.com) provides walking tours of various San Diego neighborhoods, including Ocean Beach and Hillcrest. Tours depart from designated meeting places in the neighborhood where the walk takes place. All tours are $10.

Where You Want to Be Tours (tel. 619/917-6037; www.wheretours.com) puts a lighthearted touch on its offerings, which include a walking (or biking) tour of San Diego's beach Tiki culture. Other itineraries include an Old Town power walk, a La Jolla gallery stroll, and a downtown nightlife primer. Prices start at $20.

The Gaslamp Quarter Historical Foundation offers 2-hour tours that focus on the Gaslamp's 19th-century history, every Saturday at 11am. Tours depart from the William Heath Davis House museum, 410 Island Ave., and cost $10 for adults, $8 for seniors (age 55 and older), students, and military (museum admission is included); free for children age 12 and under. For more information, contact the foundation directly at tel. 619/233-4692 or www.gaslampquarter.org.

Take a walk on the supernatural side with Old Town's Most Haunted (tel. 619/972-3900; www.oldtownsmosthaunted.com). These 90-minute walking tours through Old Town State Historic Park and environs go in search of real paranormal activity, Thursday through Sunday at 9pm (private tours are available at 11pm). The cost is $19 adults, $10 ages 6 to 12, and free for children 5 and under; cash only.

Volunteers from the Canyoneer group of the San Diego Natural History Museum (tel. 619/232-3821; www.sdnhm.org) lead free, guided nature walks throughout San Diego County. The walks are held every Saturday and Sunday (except July-Aug), and usually focus on the flora and fauna of a particular area, which might be a city park or as far away as Anza-Borrego Desert.

At Cabrillo National Monument on the tip of Point Loma, rangers often lead free walking tours. Docents at Torrey Pines State Reserve in La Jolla lead interpretive nature walks at 10am and 2pm on weekends and holidays; guided walks are often scheduled at Mission Trails Regional Park, as well.

Whale-Watching

Along the California coast, whale-watching is an eagerly anticipated wintertime activity, particularly in San Diego where Pacific gray whales pass close by Point Loma on their annual migratory trek. Local whaling in the 1870s greatly reduced their numbers, but federal protection has allowed the species to repopulate; current estimates put the number of grays at about 20,000. When they approach San Diego, the 40- to 50-foot gray whales are more than three-quarters of the way along their nearly 6,000-mile journey from Alaska to breeding lagoons in the Sea of Cortés, around the southern tip of Baja California. After mating and calving they will pass by again, calves in tow, heading back to the rich Alaskan feeding grounds. From mid-December to mid-March is the best time to see the migration, and there are several ways to view the procession.

The easiest (and cheapest) is to grab a pair of binoculars and head to a good land-bound vantage point. The best is Cabrillo National Monument, at the tip of Point Loma, where you'll find a glassed-in observatory and educational whale exhibits 400 feet above sea level. When the weather cooperates, you can often spot the whales as they surface for breathing -- as many as eight grays per hour at peak commute (mid-Jan). Each January the rangers conduct a special "Whale Watch Weekend" featuring presentations by whale experts, children's programs, and entertainment.

If you want to get a closer look, head out to sea on one of the excursions that locate and follow gray whales, taking care not to disturb their journey. Whakapono Sailing Charters (tel. 800/659-0141 or 619/988-9644; www.whakapono.us) offers two trips per day (8:30am and 1pm); each lasts 3 hours and carries a maximum of six passengers. Sailboats are less distracting to the whales than motorized yachts, but more expensive; the cruises are $75 per person (minimum two passengers), including beverages and snacks. OEX Dive & Kayak Centers (tel. 858/454-6195; www.oexcalifornia.com) leads guided kayak tours in search of passing whales. It's about a 1-mile paddle that departs daily at 1pm from La Jolla Shores and lasts 2 1/2 hours; the cost is $45.

Companies that offer traditional, engine-driven expeditions include Hornblower Cruises and Flagship. Excursions are 3 or 3 1/2 hours, and fares run $32 to $39 for adults, with discounts for kids. H&M Landing, 2803 Emerson St., Point Loma (tel. 619/222-1144; www.hmlanding.com), has 3- and 6-hour trips, starting at $25 for adults, $20 for those ages 13 to 17, and $18 for ages 2 to 12. Naturalist-led trips to the Mexican calving grounds, lasting 9 to 11 days, are also scheduled.

In La Jolla, the Birch Aquarium at Scripps celebrates gray whale season with classes, educational activities, and exhibits, and the outdoor terrace offers another vantage point for spotting the mammals from shore. Multiday trips to San Ignacio in Baja California, where the whales mate and calve, are offered in February and March, and Birch provides naturalists to accompany the whale-watching done by Flagship. Call tel. 858/534-3474, or go to www.aquarium.ucsd.edu for more information. The San Diego Natural History Museum also offers multiday, naturalist-guided whale-watching trips to Baja. For a schedule and preregistration information, call tel. 619/255-0203, or check www.sdnhm.org/education.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.