Boston has its Marathon... Pamplona has the bulls... New Orleans has Mardi Gras... San Francisco has the historic Zazzle Bay to Breakers 12k.

The 100-year old Zazzle Bay to Breakers 12k is one of the world's largest and oldest footraces, held annually in San Francisco, California. The name reflects the traditional course which takes tens of thousands of participants from the northeast end of the downtown area near The Embarcadero (the "bay" side of the city) to the west end of the city and the "breakers" of Ocean Beach. The 7.46 mile (12 kilometer) race features world-class athletes in addition to costumed runners and 'fun-loving' folks out for a great day of running and walking through San Francisco http://zazzlebaytobreakers.com.