It's hard to find a "Hardcore" location which doesn't have a shorter trespassing route (beside Henry Coe), so this final cache of the Hardcore series is designed to make you at least put in some elevation, one way or another.
A few years ago I ran across a great-looking trail climbing steeply from Morgan Territory Road to the summit of North Peak. I noticed it while looking for Mt. Diablo geocaches--GC16YAD (puzzle cache) had its fake coordinates nearby. After a little sleuthing, I found it on a planning map from the State Park service: Diablo Mines. It's the golden trail from the end of "Power Line Service Road". The trail is in as good of shape as anything on that edge of the park.
I was going to put the cache a little lower on the slope, but wanted people to hike all the way up to North Peak. So I put this high enough to entice people to keep going, and low enough to punish slackers who hike in from Mt. Diablo Summit (or Devil's Elbow). But I highly recommend a 7.5 mile loop from the parking area to North Peak, Mt. Olympia, and down East Trail and Mt. Olympia Trail back to your car. Plenty of caches along the way, and it's quite short. . .
I like easy-to-find caches, but this location had no safe edges to hide a cache under, and a trail goes right by. So I buried the cache under some light volcanic rock. There are two rock spires here--the cache is right next to the shorter one, facing the taller one. Can't miss it with that clue, please re-hide so a muggle won't notice. . .
If you like hiking as much as caching (or more!), be sure to visit all the caches in the Hardcore Hiker series. Perhaps you'll show up on the list of those who have found caches in the series. Are you hardcore?