Castle Lake Overlook is perhaps one of the best hike-to views in Siskyou Mountains as it offers a great perspective of Mount Shasta and Black Butte, and visitors can also enjoy swims in Castle Lake or Heart Lake.
Directly from the overlook you will see Black Butte rising from the earth, only to be trumped by the massive Mount Shasta right behind it to the northeast. The top has enough area to sit around, and the more adventurous may choose to look over the edge. Below the overlook, the entire Castle Lake is visible. The overlook is rather rocky, with visual evidence of glacial scoring in the rock-bed across the entire trail system. The area itself was carved out by a glacier over 10,000 years ago.
Starting from the Castle Lake Picnic Area, the trail is self explanatory. The first half mile is the toughest area on the legs, as it is more vertical, but it is by no means strenuous. This part of the trail itself is rather soft until you level out and reach the saddle at 0.6 miles. From there the trail can get confusing, as it cobwebs up the mountain side in various (wrong) directions. Do not hike directly to the overlook, as you will end up bushwhacking your way out. Instead, keep left as the trail will take you to the easternmost side of Heart Lake. The trail to just Heart Lake is a mile long, with only 575 feet of ascent. Free dispersed camping on Forest Service land is available at Heart Lake and just past the lake on the way to the overlook.
After passing Heart Lake, continue west along the mountainside. The beginning of the overlook is only 0.3 miles away after leaving Heart Lake. After passing through a small meadow you will reach a skinny trail that climbs through scree and brush before reaching a small cliffside clearing. Another skinny trail will take you higher to the peak of the overlook; there is less room for standing or sitting, there is a fantastic 360-degree view.
The hike is short and easy enough that one can safely descend after sunset. Make sure to jump in Heart Lake during the summer, as the shallow body of water will warm with the weather.