Naming a publicly-accessible wilderness area a “secret” may add an unwarranted air of mystery but the name is otherwise accurate; there are mountains and plenty of red rocks!
The Long Canyon trailhead is easy to find on Google Maps. There is a limited amount of parking, but this trail is not nearly as busy as nearby Dry Creek and Devil’s Bridge. The trail follows the creek, sloping gradually up for about 4.5 miles before ending abruptly at a cliff in dense forest. Along the way are impressive views of the canyon cliffs.
The layered red sandstone is fascinating to examine up close.
You can find a detailed description of the hike here.