Boulder County has no shortage of mountains, but that doesn't stop the crowds from hiking their peaks. For anyone who still wants to get away from the crowds by climbing a less-popular and less-accessible peak that still boasts a fun challenge and great views, then Eldorado Mountain is for you. It sits to the south of Eldorado Canyon State Park with the KBCO radio station antenna array on top. Boulder restricts public access to this area, so there is no official trail to the summit, and the private road to the radio station is private as well. Of course, that is why it is secluded compared to the nearby Bear Peak, South Boulder Peak and Green Mountain. There are several ways to the top that stay on public land.
There are many railroads that cross several flanks of the mountain, which are private property and should be avoided. To the north in Eldorado Canyon sits the former site of the Crags Hotel along the Rattlesnake Gulch Trail, which only operated between 1908 and 1913 before it burned down and wasn’t rebuilt. The Rattlesnake Gulch Trail is an excellent access point to the social trail that climbs the North Ridge to the summit, but for those wanting to avoid the entry fee, you can park along a county road at another access point just outside the state park.
To begin the traverse, start along the Fowler Trail and decide if you want to do the loop clockwise or counter-clockwise. This description will focus on taking the Mickey Mouse trail up, but you can do it in the opposite direction as well. When the Fowler Trail turns right along the canyon to access the state park, you should continue straight on the Goshawk Ridge Trail. After passing a few small access roads, you’ll see a couple short signs that describe nearby climbing routes. At the entrance to a clearing, you’ll see the Mickey Mouse Trail. It can be difficult to find without the sign. Take this all the way up and follow the boot path to the railroad track. There is no access on the other side, so find the social trail heading back into the woods on the left near the tunnel and drop back down on the other side of the tunnel.
Once at the second set of tracks, you’ll see the enormous Mickey Mouse Wall that has excellent rock-climbing. This access point is often closed during the summer (May to July) to protect raptors nesting, but is open the rest of the year. In the summer, an out-and-back up the North Ridge is a good substitute. Make your way across the tracks safely and start scrambling up the boulder field that follows the rock wall all the way up to the ridge. This is a true Class II+ scramble and should not be taken lightly.
At the top, look for small social trails that continue leading up to the left where Eldorado Mountain is. Just before making the ridge, you can see the radio antenna to the left behind you so you can orient yourself. You'll steadily climb until it flattens out, and the main summit overlook is off to the right. Find the highpoint with the rocky outcropping on that side of the summit area. After taking in the great views of Indian Peaks and Longs Peak in the distance, and the closer South Boulder and Bear Peaks across the canyon, go back the way you came until the ridge forks left and right. To do the loop, you’ll want to take the left (north) ridge instead of the one you ascended. Continue following the ridge down, and be careful as there is Class II+ scrambling and steep sections on your way down.
Eventually you’ll come to a junction with a much more clear and wide trail, which is the Rattlesnake Gulch Trail. From here it is a small loop, so you can go right or left as long as you go down. When the path levels out, go east along the canyon, which offers fantastic views of Shirttail Peak, a dramatic craggy rock wall that offers some of the best rock climbing in the world. Make your way back to the Fowler Trail and return to your car from there.