Mount Diablo is a 3,900 foot (1,170 meter) hill in Contra Costa County, California in the San Francisco Bay Area. The Mount Diablo Challenge is a bicycle race held annually on the first Sunday in October. The race begins at the Athenian School at the base of the mountain and climbs 3,249 feet (990.3 m) in 10.8 miles (17.4 km). The race draws about 1,000 cyclists each year who compete in a mass-start format, with different waves of differing ability levels starting at different times. Bicycle riders of every age and ability are represented in the diverse field, from weekend enthusiasts to top professionals. All proceeds benefit Save Mount Diablo’s land conservation efforts.