Auburn State Recreation Area ( http://www.parks.ca.gov/?page_id=502 ) In Pointed Rocks ranch (also called Knickerbocker Ranch or Olmstead trail area.) This "trail" starts at Gate 155, the knickerbocker gate, behind the Cool fire station. I don't necessarily recommend this trail, but I am adding it for completeness. The first 2 miles of the trail is a flat, 2-lane, paved road. No motor vehicles are allowed in the park, so this makes a nice bicycle road especially for families. The second 2 miles are dirt switchbacks. They are steep, exposed, hot,dry and full of star thistle. This "trail" used to be part of the Auburn cool trail, but no more. There is a feasibility study to make a new crossing at the river: http://www.parks.ca.gov/?page_id=24568 For many years there was an ongoing proposal to build a dam in Auburn. The water in the river at the bottom of this trail was sent through a diversion tunnel during the dam investigation phase. This allowed horse riders, hikers and mountain bikers to cross the river bed in a dry section. This means for a few decades hikers, bikers and horse riders could travel from Auburn to Cool or make a very long loop from Auburn to Cool and back a different route. Recently the dam project was abandoned and the diversion tunnel was closed allowing the river to flow in its banks once more. There is now no way to cross the river at the bottom of this trail unless you want a dangerous swim.