Tunnel Lake Trail is a 9.1 mile moderately trafficked out and back trail located near Nathrop, Colorado that features a lake and is rated as difficult. The trail is primarily used for hiking and mountain biking and is accessible from July until September.
Directions from Nathrop: Southern Access: Drive 15 miles west on Chalk Creek Road (Coutny Road 162) to St. Elmo. Turn south on Hancock Road (County Road 295) and drive approximately 5.5 miles. Look for Forest Road 298 (recommended for 4WD only), which is the old railroad grade to the Alpine Tunnel. Travel 2.5 miles on this road and take the trail over the tunnel to reach the trailhead for 1439.
Beautiful hike only ran into a handful of people during hike and had the lake to ourselves for a couple of hours.
Beautiful location and setting just off the Continental Divide. Hiked in early Sept. Great location, I was all along. Not many level good spots to pitch a tent. Lots of low brush around the lake making it hard to navigate around the lake. Some maps or GPS show a low trail to the Lake. This does not exist, follow the high trail around the upper rim of the CT.
This was my first ever hike in Colorado, and it kicked my ass. We did it in the middle of July, and we saw maybe 6 or 7 other people the whole time. Great views with only one real stretch of switchbacks. I wouldn't recommend it for beginners.