680 Trail via Big Rock
Approx. 10 miles & 1750ft of climbing, 1-2hrs
The 680 Trail is a nice piece of relatively easy singletrack that gives you another ride option from the Big Rock parking area (as opposed to going up to the communication towers to the north side of the road). The ride starts with a fireroad climb up Loma Alta to access 680, and ends with a paved road climb back up Lucas Valley Road to get back to your car.
The 680 Trail flows easily, isn't very steep, and does not include much in way of rocks or roots. There are some rain ruts that can throw you for a loop if you're not paying attention, especially when wet.
680 Trail is appropriate for an after-work spin, or as a stepping-stone ride for novice riders looking to get to the next level. As riders progress, they are more likely to be using 680 as a connector trail to extend their rides.