Palomar Mountain (County Road S6)

County Road S6 climbs Palomar Mountain from Highway 76 at Rincon Springs toward Palomar Mountain State Park and Caltech's Palomar Observatory. California State Parks calls it “scenic but rather steep and winding” and steers heavily loaded vehicles and anyone towing to County Road S7 from Lake Henshaw, which is longer but gently graded. There are no gas stations on the mountain, and notices of observatory closures may be posted at the S6 summit, about 4.2 miles below it.