Looking north, down on Glacier Lake from the saddle between two of the Black Buttes. The highest Black Butte is 8,028 ft. From this ridge, there is a great 360-degree view of the northern Sierra and beyond.
This is one of the most convenient and prettiest hikes within easy driving distance from Sacramento and the Central Valley. A favorite!
Looking northeast from the ridge of the Black
Buttes, overlooking Glacier Lake
While my topo software says it's about 3.3 miles one way, it feels like about 10 miles round trip, from the Grouse Ridge parking lot. There's moderate elevation gain, maybe 900 ft. There's also the option of another 800-ft. climb to the top of one of the Black Buttes, overlooking the lake and providing excellent 360-degree views of the surrounding mountains. The trail is good; the climb up the Black Buttes is cross-country, however, with a little rock-scrambling likely.
Take I-80 east, about 85 miles from Sacramento, to Highway 20, and turn north toward Grass Valley. 5 or 6 miles along Hwy. 20, turn east on the Bowman Lake Road, for 6 miles. Just past the PG&E camp, turn south (right) on the Grouse Ridge Lookout road. The road becomes dirt & gravel. While 4WD isn't required during the summer, it's good to have a vehicle with relatively high clearance...lots of potholes, rocks, bumps. In spring/early summer or after an early snowfall, don't risk it in anything but 4WD. It will probably take at least 25 min. to drive the last 6 miles on the dirt road. Keep left, beyond the Grouse Ridge Campground, to the trailhead parking lot. While one can also park and hike from Carr Lake, further along the Bowman Lake Road, it adds another 4 miles round-trip to the hike, and it's not as attractive a hike. Carr Lake is also often crowded. I recommend using the Grouse Ridge parking lot as your trailhead.
In addition to the beautiful scenery along the trail, with granite outcroppings, wooded glades and the occasional mountain meadow, Glacier Lake is a lovely small alpine lake tucked under the imposing Black Buttes. It's a great place for an admittedly-chilly swim, clean & clear. If you decide to climb the Black Buttes, with the frequent good visibility, you'll see peaks from Mount Diablo to Shasta.
Carry 1 to 2 quarts of water, depending on the temperature. There's almost always running water available in many little streams, but there are also summer-grazing cows. It's probably wise to treat even the running water. Carry extra clothing to the trailhead and decide there how much to put in your daypack. There are often thunderstorms in the summer, and occasionally late or early snowfalls. Check the weather before you leave.
Here's a rough map of the hiking route (111 KB). The old-ish topo map does not indicate the new-ish trail to Glacier Lake, so I've sketched it. No guarantees this route is absolutely accurate. Here's another Glacier Lake picture.