This is a much longer hike than Lake Lagunitas -- about 3.5 miles around the lake. There are two very different sides to this lake -- the shady side and the very sunny side. The trails are for hikers only, no bikes allowed on almost all the hike route. There are a number of fishing spots around the lake, so you will see folks fishing along the way.
This hike starts from the Lagunitas Picnic Area part of the parking lot. The shadyside trail is a single track well worn trail just across the bridge from the picnic area.
This shadeside trail stays a bit away from the lake in parts, but you can almost always see the lake with peek-a-book views through the trees.
On the southside of the Lake there is a open bay area where we say a white crane (?) hanging out near the shore.
The trail is very well maintained with a bridge or two that crosses some of the natural creeks feeding the lake. There is one intersection on this side of the lake with the lower berry trail.
The shadeside trail is well named with almost all shade for the 1.4 miles. I think most people do this trail as an out and back since its very cool on a hot summer day. We saw at least 10 groups of folks on this side of the lake on a very late Saturday afternoon.
The shadeside trail ends at the Bon Tempe dam - the rest of the hike is very much in the sun so be sure to bring water and sunglasses. From the dam you can see Alpine Lake below and the Bon Tempe parking lot.
After crossing the dam, you can take a shortcut if the water level is low. Otherwise head down toward the Bon Tempe parking lot and reconnect with the Sunnyside trail.
The sunnyside trail is well named - its almost all sun for a mile. But it has a really nice and different feel from the shadyside trail. You get more views of the lake, Mt. Tam and the interesting contrast of the desert-like shore and the blue water of the lake.
The sunnyside trail ends up at the Sky Oaks Road, just continue on the road around the lake.
After passing a restroom and observation deck, there is a good shortcut at the telephone pole along the road. This shortcut trail connects with the Pine Point trail. Keep to the right to keep on the trail closest to the lake.
The Pine Point trail is a less travelled trail compared to the Shadyside and Sunnyside trails - but its well worth the trip as you get very close to the lake in parts with some cool trees and inlets along the way. There are a number of unmarked intersection on the remaining part of this hike, if you want to stay close to the lake just keep right at all intersections.
We saw a couple lizards and a snake along the hike.
The Pinepoint trail then leads to a large dirt road which heads back to the north end of the Lake Lagunitas parking lot.
There is one last intersection, but again, just keep to the right closest to the lake for the way back to the parking lot.
Another option is to start on the Sunny side of the lake and do this hike in reverse -- so you end the hike on the shadeside trail. Its probably a better option on hot days, so you end the hike in the shade. If you do that option, just look for the start of the hike by this pipe structure.
This is another great hike in the Marin Municipal Water District and a bit more enjoyable than Lake Lagunitas. The trails are pretty much unmarked, but its hard to get lost as you just stay to the right and choose the trails closest to the water. In any case, the MMWD has a nice PDF map available of the area.
View Bon Tempe Lake in a larger map
Basics:
Area - Marin Municipal Water District's Mt. Tamalpais Watershed
Trails - Shadyside trail => Bon Tempe Dam => Sunnyside Trail => Sky Oaks Road => Pine Point
Map - Visitor Map
Length - 3.5 miles Loop hike (Easy hike, but can get hot on sunny side)
Trail - Well maintained dirt road and trail
Dogs - Yes, on a leash
Bikes - No (except on road and dam)
Views - Views of the Lake and Mt Tam along the way
Getting There - See the end of this post
Fee - $7 per car at Park Entrance Pay Station ($20s not accepted)
Weather - Some sunny spots, otherwise mostly in the shade
Other Trails - Yes, connects to Berry trail, Rocky Ridge Trail,
Facilities - restrooms and water at the trailhead/parking lot.