3. San Diego

The city of 1.2 million is flat and sunny with 850 miles of trails and lanes that take riders from shore to canyons—what's not to love? In fact, San Diego tops most lists of best cycling cities of more than one million people and it may one day surpass Portland (think constant temperature between 50 and 80 degrees—and no rain) as the city has added 300 additional miles of trails in the last three years alone. The Bayshore Bikeway, which conveys pedalers along a 24-mile oceanfront corridor, may be North America's most sublime trail, though escaping to mountain trails is also a snap. Try to visit during August's Midnight Madness ride (the party starts at PM.), and also make sure to visit the downtown velodrome and Olympic Cycling Training Center.

For more information: San Diego