Mt Olympia hike

Part of Mt Diablo State Park

Jan 12, 2014

I'm posting a little trip report mostly because I couldn't find too much good information ahead of time. Hopefully this will be useful to others.

I found a brief description of this hike in Weekend Sherpa. It's a ~6 mi hike up and down Mount Olympia on the back side of Mt Diablo Park. The climb has ~2,000 ft of elevation. It's not even gains though, so once you really get climbing it averages about a 20% grade with brief blips at or above 30%. The trail is also very narrow at spots making footing a little tricky. At no point did I feel it was dangerous beyond the slight risk of twisting an ankle though. You can see the route and elevation profile on Strava.

It was a fun trail. Mostly exposed, there were some great views. The geology is interesting with several outcroppings that lent character to the route. Short twisty trees and burned out areas also add color and interest, though much of that may have grown back by now. Not terribly popular, as I think it's probably pretty difficult to find.

Summit Marker on Mt Olympia.

How to get there

SummitPost has a brief description of the trailhead / parking:

Start from the Marsh Creek Road trailhead (elevation 900 feet, there is no sign that says Mount Diablo State Park but none that says "private property, no trespassing" either). Pass under the gated entrace, and follow a dirt road around a small hill on the right.

The trailhead parking appears to be on the South Side of Marsh Creek Road, but it is poorly marked. I'm not 100% sure this is the correct spot, though I think so. It's more of a dirt pullout with a gate across it. There are a couple of mailboxes and when I was there some trash cans had been set out. The gate has some security cameras and signs. It looks like private property except that one of the gates has a Mount Diablo State Park sign on it, presumably new since the SummitPost writeup. There are no parking signs, but similarly no "no parking" signs either. When I arrived there were 2 other cars, 3 others when I left. Here's what it looks like on Google Streetview:

Street view image of the 'parking lot' for hiking Mt Olympia.

I played around and found out that at least with Google Maps / Navigation, an address of 9850 Marsh Creek Road, Clayton, CA will take you to the exact spot you want to start.

The trail

The maps available online also don't have most of the trails marked. Google Maps doesn't have them marked, even Mt Diablo's park brochure doesn't show the trails. The map you really want is the Mt Diablo Interpretive Association topo. I bought mine at the Fremont REI on the way up. Here's a quick view of that section of the map:

Map showing the trail to Mt Olympia.

You start out walking about a half mile down the unmarked Three Springs Road from the parking lot in the Northeast before coming to Mt Olympia trail markers. The trails are well marked, fortunately. I continued on the road as far as I could and then took the Olympia Trail to East Trail to Mount Olympia. This is a steep but pretty route. On the way back I took the longer route around via Mount Olympia Rd. It's a fire road, not as attractive, but easier on the knees for the descent.

Some of the vegetation on Mount Olympia Rd has hidden the trail sign at the intersection with Olympia trail. It shouldn't be hard to see the trail, and if you get the gate, you've gone too far, but something to watch out for.

There is also a trail option south from Olympia about a mile to North Peak. I didn't go that route on my first trip as the peak was shrouded in clouds and I was getting chilly at the top of Olympia as it was. I did however return in Dec 2015 with better weather and hike to North Peak. It's a nice addition to Olympia if you want more of a challenge, but Olympia is definitely the prettier peak of the two, as North Peak is covered in radio towers and looks like a construction site.