Scenic by-the-bay bicycle routes and California's favorable climate makes sight-seeing on two wheels fun.

San Diego: One of the city's most popular rides is a 26-mile loop around San Diego Bay on mostly flat terrain, using the ferry to access Coronado Island and the Silver Strand.

The Bayshore Bikeway is a pretty 24-mile, 2.5-hour ride with no significant hills, most of it along bike lanes or bike paths. The scenery is rich and varied and you can stop by the Chula Vista Nature Center on the way.

Route directions and a fact sheet are at www.efgh.com/bike/rsdbay.htm. For guided bike tours and bike hire: www.sdbikeshop.com.

San Francisco: The famous Bay Trail follows the shoreline from downtown San Francisco to Sausalito. Along the nine-mile trip: the Palace of Fine Arts, the Presidio, and Fisherman's Wharf. Riders have the choice of returning via ferry. Another highlight: crossing the Golden Gate Bridge using set-aside bike lanes.

No hassles with traffic or parking, or waiting for buses. Bike and Roll, bikeandroll.com, rents bikes from four locations and offers daily guided tours. From the Golden Gate, more advanced cyclists can access the Marin Headlands, Muir Woods, and 2,572-foot Mount Tamalpais. For more bike-friendly cities, see National Geographic Traveler's list at www.blogs.nationalgeographic.com/blogs/intelligenttravel/2010/