Take Castle Creek from the roundabout just west of the center of Aspen. Drive 12.5 miles (paved) to the Castle Creek trailhead. To the right, Forest Road (FR) 102 continues all all the way to 12,800'. Good-clearance passenger cars can drive about 1 mile up this road to reach the dispersed camp sites along the road. If you want to shorten your hike by parking higher, you must have a 4WD vehicle with good clearance. From the lower trailhead parking area, proceed 1.3 miles to a river crossing. In spring and early summer, this crossing is a challenge for some 4WD vehicles. Continue another 1.7 miles up FR 102 to a junction. Left will take you up the nasty Pearl Pass 4WD road. Staying right will keep you on the Castle Creek 102 road. If you drove up this far, there are a few parking spots near the junction. The road gets worse as it ascends into Montezuma Basin all the way to 12,800'.
This route assumes a start at the FR 102 and Pearl Pass road junction (11,100') - Photo #1. The topo map shows the route from the road junction. From 11,200', hike 2 miles up the road (Photo #2, Photo #3 and Photo #4) to 12,400' below the Montezuma Mine and continue (Photo #5) for another 1/2 mile to the end of the road at 12,800' - Photo #6. Photo #7 looks down on the road. From here, you are looking southwest at a steep slope that has snow through much of the year. Cross the water to your left and get on the side of the hill before continuing right over to the slope. Photo #9 shows a couple of ways to ascend this area. Climb 500' up the slope by crossing the snow or climbing the loose talus - Photo #10. If you are hiking in June or July, there will probably be snow to 13,200' or so.
Near 13,300', enter the large basin north of Castle - Photo #11. Castle is ahead to the south. Look left to the Northeast Ridge and locate a trail that climbs the rocky slope leading up to the ridge - Photo #12 and Photo #13. This slope usually melts out in late spring or early summer. Hike over 300' to reach the ridge crest near 13,700' - Photo #14 and Photo #15. Continue south on the trail as it approaches some rough sections on the ridge - Photo #16 and Photo #17. Now the fun begins. Follow the broken trail along the ridge through minor scrambling sections with some loose rock - Photo #18. This route is mostly stable if care is taken in the steep sections. Near 14,000', come to point where you can preview the final 250' to the summit - Photo #19.
Drop down to a small saddle and start up the final pitch. Continue winding up through delicate rock toward the summit. Photo #20 looks back on the route from this final pitch. There are a couple of rock sections that may slow down your route finding but there is an easy way around each obstacle. This pitch is a bit steep and loose but still Class 2 - Photo #21. The climbing doesn't last long and suddenly you are on the summit. Photo #22 looks down on the route, and Photo #23 plus Photo #24 are views from the top.
The FR 102 road past the 9,800-foot trailhead turns nasty after a mile or so. If you don't have a good-clearance 4WD vehicle, park low. There is parking for a few vehicles at the Pearl Pass junction. Parking here will allow you to get over 3,000' of gain on your hike. The rock on Castle is loose - be careful. IMPORTANT: This route enters the Maroon Bells - Snowmass Wilderness area. Wilderness areas have special regulations and restrictions for party size, dispersed camping, campfires, etc. Also, dog owners should read the wilderness information carefully because some wilderness areas prohibit dogs to be off-leash and/or limit how close dogs can be to lakes and streams. If you have questions about the Wilderness area, please contact a U.S. Forest Service office for the National Forest(s) listed above.