Organized Tours

Centre City Development Corporation's Downtown Information Center, 225 Broadway, Suite 160 (tel. 619/235-2222; www.ccdc.com), offers free downtown bus tours the first and third Saturdays of the month at 10am and noon. Reservations are recommended 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 models of the Gaslamp Quarter and the downtown area. The office is open Monday through Saturday from 9am to 5pm.

Amphibious Adventure

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 (except Mon in winter), from 10am to 4pm (till 5pm in summer). The cost is $30 for adults and $15 for kids 4 to 12. Free for children 3 and under. For information and tickets, call tel. 619/298-8687, or visit www.historictours.com.

Bus Tours

Gray Line (tel. 800/331-5077 or 619/266-7365; www.sandiegograyline.com), has a plethora of outings, including a daylong Grand Tour that covers San Diego, Tijuana, and a 1-hour harbor cruise. There are also trips to the San Diego Zoo, Wild Animal Park, LEGOLAND, SeaWorld, Disneyland, Universal Studios, Tijuana, Rosarito Beach, and Ensenada. Prices range from $32 for the 4-hour City Tour to $60 for the Grand Tour (prices range $16-$28 for children 3-11). Multiple tours can be combined for discounted rates, and passengers can be picked up at most area hotels.

Not to be confused with the public transit trolley, the narrated Old Town Trolley Tours (tel. 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; and you can hop off at any one of 10 stops, explore at leisure, and re-board when you please (the trolleys run every half-hour). Stops include Old Town, the Gaslamp Quarter and downtown area, 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). The tour costs $30 for adults ($15 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 4pm in winter, and from 9am to 5pm in summer.

City Sightseeing (tel. 619/296-2400; www.citysightseeing-sd.com), which operates in dozens of cities around the world, provides a similar service. Narrated tours are conducted aboard double-decker buses that continuously loop through the city, offering on-and-off privileges at Old Town, Balboa Park, the Gaslamp Quarter, and five other spots. The full tour is about 2 hours, and your ticket is good for 48 hours; tours commence in Old Town, from City Sightseeing's office at 2415 Old Town Ave. Day tours are $25 to $30 for adults, $15 to $20 for children age 4 to 12, and free for children 3 and under. Night tours are also available ($20 adults, $12 children). Coronado is not included in these tours, but passes for the Coronado ferry are included in some ticket prices.

Walking Tours

Walkabout International, 2825 Dewey Rd., Ste. 202, 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 hike in the mountains takes place most Wednesdays and Saturdays.

Urban Safaris (tel. 619/944-9255; walkingtoursofsandiego.com) provides walking tours of 10 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 of the quarter 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 above), students, and military (museum admission is included); children age 12 and under are free. For more information, contact the foundation directly at tel. 619/233-4692 or www.gaslampquarter.org.

Volunteers from the Canyoneer group of the San Diego Natural History Museum (tel. 619/255-0203; www.sdnhm.org/canyoneers) 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 the 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. And guided walks are often scheduled at Mission Trails Regional Park.

Touring San Diego Haunts

Those who want to take a walk on the supernatural side can stroll through Old Town with self-proclaimed "ghost hunter" Michael Brown (tel. 619/972-3900; www.oldtownsmosthaunted.com). He leads tours in search of real paranormal activity Thursday through Sunday at 7, 9, and 11pm. The cost is $25 adults, $15 children 6 to 12, and free for children 5 and under; it includes admittance to the Whaley House. Ghostly Tours in History (tel. 877/220-4844; www.ghostlytoursinhistory.com) leads walking tours through both Old Town (Thurs-Sat 7 and 8:30pm) and the Gaslamp Quarter (Fri-Sat 7:30pm). The cost is $10, free for children under 5. (The Gaslamp tour may be inappropriate for small children.)

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 their parade.

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. Classic Sailing Adventures (tel. 800/659-0141 or 619/224-0800; www.classicsailingadventures.com) offers two trips per day (8:30am and 1pm); each lasts 4 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. The cost is $60 for a single kayak, $110 for double.

Companies that offer traditional, engine-driven expeditions include Hornblower Cruises and San Diego Harbor Excursions. Excursions are 3 or 3 1/2 hours, and fares run $30 to $35 for adults, with discounts for kids.

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. Multi-day 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 San Diego Harbor Excursions. Call tel. 858/534-7336 or go to www.aquarium.ucsd.edu for more information.

The San Diego Natural History Museum also offers multi-day, naturalist-led whale-watching trips to Baja. For a schedule and preregistration information, call tel. 619/255-0203 or check www.sdnhm.org/education.