The western Lost Lake trailhead is at the end of a short paved side road to the petrified tree
, forking off the highway 1.5 miles before Tower Junction. The tree is a vertical fossilized redwood trunk about ten feet high, enclosed by a fence to protect it from vandalism - two similar trees nearby were removed piecemeal by early park visitors, though stumps can still be seen. From the parking area, a level trail heads southeastwards along the floor of a shallow treeless valley, reaching the end of Lost Lake after 0.7 miles. A second path runs due east over partly wooded land then down a slope to the alternative trailhead, located behind the log cabins of Roosevelt Lodge
. If starting from here, non-residents need to leave vehicles at a pull-out along the main road rather than at the lodge itself. The trail to Lost Lake from the lodge is a little more challenging than the western route since it climbs 300 feet up a steep hillside, but also better since gaps in the trees allow distant views over Pleasant Valley
to the north, and the path passes close to 40 foot Lost Creek Falls
- a short spur leads up a narrow ravine to the base of this secluded waterfall, which is quite forceful in spring but a mere trickle in late summer. The main trail zig zags up the steep slopes through tall, widely separated Douglas fir trees, reaches the edge of the plateau after half a mile, then joins another path from Tower Fall campground. Lost Lake appears after a short (0.2 mile) walk across marshy meadowland; the path continues right along the north shore and on towards to the western trailhead.
Map of the Lost Lake Trail