I've wanted to do this hike for a while. The Mt. Diablo Grand Loop hike is a route that takes you around the peak of Mt. Diablo, with a little trip up to the summit. This is an ambitious hike, with about 2500 feet of elevation change and 7 miles of hiking. My mileage includes some wandering around on the summit, and some general meandering. Other accounts of this hike have the mileage pegged at about 6.5 miles.
Most of the hike is on wide, fire road type trails. There are a few sections in the last 25% of the hike that are on narrower, single track trails.
One of the locals you'll meet on the trail...
Here is what I suggest to prepare for this hike:
Bring a lot of water. You will be climbing some steep hills, and in the sun for long periods of time. Bring enough water for the entire circut. There is water at the start and at the summit, but never hike without carrying water.
Bring enough food. There is nothing better than enjoying lunch under a beautiful Oak as you reflect on your hike. Have snacks and plan on eating every 1.5 miles, and drinking as conditions require. As I become absorbed in the hiking and photography, I sometimes forget about eating and keeping hydrated. I made a rule for myself to eat and hydrate at least every 1.5 miles. This will help you avoid a crash when you really need the energy, and help you stay strong and alert. Some of these trails are precarious, and you'll want to be sure you're operating at your peak.
Bring a Map. You can download this free one, get one in the park (I never count on that) or order this excellent map before your hike. You should really order the map, because you're going to become addicted to hiking around this beautiful park. (Update, the free map I linked to above is the only one offered by the state, but I've been told that it is no longer totally accurate. They hand out an updated map when you go through the gate, but I would strongly urge you to order the MDIA map, as it was just updated.)
Note: This is a rugged hike, with steep climbs, precarious trails and potentially harsh conditions. Be prepared and make sure others know your route. This is not a hike for small children or deconditioned people. If this hike tempts you, but you are uncertain of your abilities, please start out slowly and build your strength and endurance on easier hikes. Mt. Diablo isn't going anywhere, and this hike will be there when you're ready!
This is the view from the parking lot where you'll start. You're up pretty high, but don't worry, you still have some climbing to do!
Route:
Start at the Juniper Campground. The park opens at 8am. If you get there before it opens, you can pay the $10 fee at the gate and put the reciept on your dash. Otherwise, I would also recommend camping in the Juniper Campground. This is a beautiful site, and I plan on doing this soon myself.
Start on Deer Flat Road
Look for this sign to start the hike
You'll go a short distance, past a bathroom, and you'll see this sign:
This will let you know that you're on Deer Flat Road. The trail markers on Mt. Diablo show your current trail in small letters at the top, and an upcoming trail in larger print below. So, as the sign above shows, I was on Deer Flat Road, headed toward Mitchell Canyon road. Kind of confusing if you don't actually read the sign, but you wouldn't do that, right?
Here are some scenes from Deer Flat Road:
I like the mysterious drop offs you see as you hike this trail.
Ah, the views from up here...
The trail snakes its way along ridgebacks and hillsidesThen, you'll get to Deer Flat. This is a nice place for your first break, if you haven't taken one yet.
The sign at Deer FlatAt Deer Flat, take a right on to Meridian Ridge Road. (The sign will say Meridian Ridge Road to Murchio Gap.)
Here are some scenes from this part of the hike:
You'll cross a stream along this trail. 
Manzanitas are common here, and the erosion shows a colorful root system.
Meridian Ridge Road will eventually go left, but go straight and stay on Prospector's Gap Road. Look for this sign:
Follow this sign and get on Prospectors Gap Road
As you hike up Prospectors Gap Road, you'll see a sign for Big Springs.
This is a very short little trail through overgrown scrub oak that leads in to a little clearing next to a stream.
Stream at Big Springs
A couple of trees that posed for me at Big Springs
After you leave Big Springs (just a side trip, you don't have to visit) continue on Prospectors Gap Road. Here is where the fun starts. Take the climb slowly, pace yourself, and take deep breaths. There is some real beauty in this section of the hike, so pause often, take it in, and feel your heart beating in your chest. You're going to climb about 1000 feet here. You'll feel it in your glutes tomorrow, but for now, simply concentrate on proper footing for each step. Also, be aware for bikers flying down this road. I saw the end result of a biker fall on this hike. Luckily it wasn't too serious, but don't trudge up this trail with your head down. Pay attention to oncoming bikers and your own footing.
Here are some scenes from Prospectors Gap Road:
Rocky hillside across the valley
Biker starting his descent down Prospectors Gap Road
Looking down from Prospectors Gap Road
You'll soon find yourself at Propectors Gap. There are a number of trails intersecting here, but you'll want to go right, on to the single track North Peak Trail. Look for this tree and sign:
North Peak Trail is between the big tree and the sign. I really enjoyed this section. It's still a climb, but you'll like the single track trail as it meanders through Pines, Oaks and Bay trees. Here are some scenes:
Some sections of this trail are narrow and on a steep slope, pay attention.
When you fatigue, rocks and roots can trip you up. Keep your feet up.
I could only see this ray of sunlight through my camera lens.
Still climbing...
You're getting closer, the building you see is the summit.
Can you spot the trail runner? You'll be on this trail too. At this point, you might see a few more hikers and bikers who have come down from the summit and are just wandering around. A few people sit and enjoy the view from here.
At the Devil's Elbow, go right up the Summit Trail:
Keep following the Summit Trail. You might see quite a few people here who have driven up to the top. Not you, you climbed up!
A nice little trail with Oaks and Manzanitas brings you up to the top.
Whoo Hoo! You made it to the top!
The Museum at the summit.
At the museum, you can use the bathroom, buy a beverage and enjoy the views. Remember, you still have to hike back to the starting point. It's about 1.25 miles, but it's down hill through a nice, single track trail.
The final part of your journey is to head down the Juniper Trail. Head to the west end of the lower parking lot, and find the trailhead for the Juniper Trail.
Trail marker for the Juniper TrailShortly, you'll cross the road and reconnect with the trail on the other side. It's clearly marked.
Reconnect with the Juniper Trail across the road.Almost there! Enjoy this part of the hike. Take long, stretching strides as you may have stiffend while you rested at the summit.
Here are some scenes of the Juniper Trail:
Nice, Oak lined trail
Almost done, just a few more pictures to take! (Photo by Lucien Smith)
And, you made it! Find your car, drive home and relax, you've earned it.
Route:
- Start at Juniper Campground
- Go straight on to Deer Flat Road (See this past the bathroom)
- When you reach Deer Flat, go Right on to Meridian Ridge Road
- Stay Straight on to Prospectors Gap Road (Don't go left)
- At Prospectors Gap, go Right on to the North Peak Trail (You'll see the sign next to a big Oak. Follow the arrow that points to the trail, between the Oak and the sign.)
- At the Devil's Elbow, go Right on to the Summit Trail
- Go through the parking area, watch for cars and bikes, continue on to the Summit Trail
- Summit! (Enjoy yourself and take a break).
- Head down to the west end of the lower parking area. As you face the parking area, the Juniper Trail is on your left.
- Follow Juniper Trail back to the start (You'll cross the road at one point early on, but the trail continues just on the other side of the road.) By the time you're on this part of the trail, you might be a bit fatigued. The good news is that Juniper Trail is down hill.
- Finish, and celebrate a nice accomplishment!
Distance - 7.88 miles (This is what my Garmin GPS watch indicated, but I've read in other places that if you stay on the trails and don't meander around the summit, like I did, you'll end up going about 6.5 miles.)
Elevation change - ~2500 feet
Trail Map (If you like hiking in Mt. Diablo, buy the map on the Mt. Diablo Interpretive Association website).
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