Submitted by Josh Grant:
This is the be and and end all loop in California's newest National Park, Pinnacles NP. You get to hit all the big points, the reservoir, the high peaks loop with it's magnificent stair work, both sets of caves, both sides of the park, east and west and you get to do it all as a wonderfully difficult loop. Bring a flashlight/headlamp because the caves (especially the Balcony cave) are dark. If the caves are closed for bat pupping, there are bypasses around both. But try to time it so the caves are open, they are a cool experience but probably slower than going around if you're doing it purely for speed. Cave status can be found - https://www.nps.gov/pinn/planyourvisit/cavestatus.htm
Starting at the Bear Gulch Day use area, there's a trail head and sign for Bear Gulch Caves, Reservoir and High Peaks Trail to the southwest of the bathroom. Take this (unnamed?) trail to the southwest where it connects with Moses Spring Trail. Stay on Moses Spring Trail (left) at the next intersection, the right will take you on a shortcut up to the High Peaks Trail, but you'd miss the first set of caves and the reservoir and you don't want to miss those. Power on your light source and push on up through the Bear Gulch Cave, this one is pretty tame and easy to navigate. Once you're out of the end you are basically at the reservoir which is a neat place to see on a calm day in the reflective morning light.
Get ready to grind though, because you're about to get on the Rim Trail headed up to the High Peaks trail and get most of the elevation gain out of the way. The neat thing about this section is you can see the High Peaks section almost the whole way and you get that anticipation going. It's a grind but it's a pleasant uphill, very runnable. Turn right at the High Peaks trail just about 2 miles later and enjoy the narrow stair cuts, amazing views and occasional condor sightings up here. A bird with a 13 foot wingspan is both beautiful and a bit unnerving to watch fly honestly. The High Peaks section is just under a mile, but it's slow going, so just enjoy it.
When you get to the end, turn left down Tunnel Trail to Juniper Canyon Trail. The top sections have too many switchbacks to gain much speed on but once you're lower in the canyon this is one of the few places along this loop where you can really let it rip. There's water and a bathroom at the bottom in the parking lot there if you need it, if not continue on to the right on Balconies Trial and keep on ripping on this wonderful single track. The only intersection here is with the Balconies Cliffs Trail if you want to bypass the caves, it's about twice as far but much faster. Again, your choice, this section of caves is much longer and a little intimidating because of how pitch black it is and a little hard to navigate. Look for the arrows painted in the rocks, and have some confidence that if I can do it, you can too, I have faith in you. Take the caves if you can, it's a really unique, though slower experience.
Once you're out of the cave you follow the West Fork of Chalone Creek for a little over a mile, this is a great running section here to make up time spent in the cave. Take the next two rights, to get onto a section of the High Peaks Trail that you haven't seen yet. This section is steep and exposed and can be warm, get up it to the intersection with Condor Gulch and go left, downhill back to the Bear Gulch Parking lot.
Route ends at the sign just before the bridge into the parking lot (sign says Condor Gulch Trail to High Peaks Trail 1.7).
Summary - Bear Gulch Parking lot start, head to Bear Gulch Caves/Reservoir, take Rim Trail to High Peaks Trail to Tunnel Trail to Juniper Canyon Trail to Balconies Trail to Bench Trail to High Peaks Trail to Condor Gulch and end. It sounds confusing but if you see a map it makes sense how to flow through it: https://www.nps.gov/pinn/planyourvisit/maps.htm.
Pro tip: show up early so you don't have to take the shuttle in/out of Bear Gulch. Before 8am and you usually get front row parking with no problem, plus more reasonable temps in general.
12.6 miles / 3000 feet elevation gain
Clarification: The caves are not "required", and it's certainly faster to do this route without them, but you definitely get style points for doing the caves!