The trail begins at Lake Diablo, which is a magical, turquoise color. It is, however, a bit too cold for swimming! The trail will lead through various landscapes, including Douglas firs and rainforest with plentiful ferns, rocky areas, and really lovely views of the lake and surrounding majestic mountains. Along the way the rewards include stunning views of Pyramid, Snowfield, Davis and Colonial Peaks, as well as Jack Mountain. The trail leads along the top of a gorge and from there waterfalls and the blue-green glacial waters of the lake can be seen. This is a pleasant, fairly easy hike with not too much elevation change, good for kids and for dogs--take note that dogs aren't allowed on trails in North Cascades National Park, but they are allowed here. The Diablo Lake Trail is actually in the Ross Lake National Recreation Area adjacent to the park boundary. Kayaking and canoeing are fun activities here, as well, and there are camping possibilities. Colonial Creek, Thunder Point, and Hidden Cove campgrounds are all nearby. Diablo Lake is really worth a day trip if you are in the Seattle area - the scenic drive from Seattle is also truly beautiful.