Run: Lucas Valley Open Space Preserve (Big Rock)

Bay Area > Marin > Lucas Valley Open Space Preserve

8.4 miles // 1,450 feet vertical gain//loss

Area Map

This is a great run for:

-I can’t recommend this run as we did it…

-The trail beginning at Big Rock (described at the end), however is great for a good shortish climb (<5M with about 1000′ of vertical gain/loss) and highly recommended


To the Big Rock Variation (recommended): 101 to Lucas Valley Road Exit. Take Lucas Valley Road until you see a really big boulder on your right hand side. You’re there. No restrooms.

To the variation done and described here: 101 to Lucas Valley Road Exit. Take Lucas Valley Road 3.4 miles west to turn right on Westgate. Turn right onto Creekside road. Park on the road near the gate. No restrooms.

It’s always incredible to be reminded that after years of making it my business to find and run trails all over the place in the Bay Area, there will ALWAYS be more to explore.

I let my wife call the destination for this one, and she did a great job of finding us something new and beautiful – at least mostly…

The open Space Gate. Park here.

While there were a few web reports of an out and back run starting from Big Rock, we wanted a few more miles, and cobbled together a loop beginning at the base of Luiz Fire Road,turning west on Big Rock Ridge Fire Road, and taking what the official map calls the Big Rock Trail/Bay Area Ridge Trail (though this name doesn’t appear on other quads that I referenced), then finishing by running down Lucas Valley Road to return to the car. This is a very suboptimal loop for a few reasons.

First, you begin with Luiz Fire Road and its 15% grade for two miles. You are not running this. Seriously, nobody is running this. Actually scratch that: about halfway up I got the idea that somebody should hold a race simply from the gate to the crest of the ridge. This would be perhaps the most brutal 2 mile race ever conceived. Anyway, as I said – you’re not running this. While Luiz Fire Road is a fine walk, we wanted to run.

We were hopeful that we might run consistently once on the Big Rock Ridge trail. While it looked promising on the topo, this too proved less than great running, though it’s at least within the realm of possibility. Footing is rocky and sometimes insecure.

You too can enjoy visibility like this…

On Big Rock Ridge Fire Road

Eventually you’ll come across some moderately post-apocalyptically-creepy antenna towers and then a bit later after that you’ll see what looks to be an old bunker of some kind (?), but overall the ridge is forgettable (at least with the visibility that we had, which approached zero). A feature of Lucas Valley Open Space preserve is the number of easements granted from private landowners. In practice, this just means you need to open and close a few gates along the way. After a gate next to a little shed, you’ll see the character of the trail change quickly.

From a very inauspicious beginning, this trip got better, fast.

From the shed/gate, the trail trends to gently downhilling singletrack, and IT IS GOOD. The trail switches back and forth and is totally rippable – easy grade and good footing.

Mixed Oak and Chapparal

A stand of Oaks.

From here, keep smiling and running downhill until you arrive at Big Rock.

We, like total idiots, chose to run back to the trailhead along Lucas Valley Road to complete a loop. Do not do this. Lucas Valley road is full of blind turns, has absolutely no shoulder in places, and is a truly dangerous stretch of road to run.

THE BOTTOM LINE: Park at Big Rock and do an out-and-back up Big Rock Trail to the ridge. It clocks in at a bit under 5 miles roundtrip with 1000′ elevation gain/loss. There’s a reason this is the first web page to describe the loop we did – it sucks.