This is a difficult out and back trail to Snow Lake in the Alpine Lakes Wilderness.
It is heavily trafficked but worth the crowds. You'll hike in through beautiful forest, up and over a ridge with astounding views around you, and end up at an amazing alpine lake for not much effort compared to most of the lakes in the region.
For some more solitude, continue hiking around the edge of the lake and onto Gem Lake, or the Wildcat Lakes. These lakes are a bit higher in elevation than Snow Lake but due to this you'll lose the crowds a bit the further you go.
Park in the Alpental Ski Area parking lot (to the left of the road) and head across the road to the trailhead (you want to go the opposite direction from the covered bridge crossing the river). Fill out a self issued wilderness permit before heading onto the trail from here.
A Northwest Forest Pass is required to park, or you can pay the day parking fee of $5. There are toilets and a picnic table at the trailhead.
See the Washington Trails Association webpage here for more information.