The Summit Lake Trail is a lovely 2 mile round trip trail from the Interstate 80 rest area on Donner Summit to Summit Lake. You are not supposed to park at the rest stop but can have someone drop you off or you can park off the Castle Peak Area/Boreal Ridge Road exit. This does add another couple of miles to your hike.
You start this hike from about 7200 feet but there is only about 200 feet elevation gain in the hike. It does go up and down a bit which makes it seem like more than 200 feet gain but it is still a pretty easy hike. It takes you through conifers,over granite , through a large meadow and finally to a beautiful small lake. The trail goes around the lake if you are so inclined. You pass a couple of little creeks on your way to the lake if you are hiking in June - probably early July. By August, these have dried up. Even then, you will see wild flowers blooming around these damp areas.
I found the interesting shelf fungi shown in the photos growing on trees near the lake on two different years. These were much more interesting than the usual white fungi that you see more frequently. You might watch for them if you are near the lake.