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'.
From the 2WD trailhead, drive or hike 1.3 miles to the stream crossing near 10,200'. If you cannot drive beyond this point, there is a footbridge on the left. Continue about 1.5 miles up the road to a bridge crossing. Follow the road less than 0.25 mile up a steep hill to reach a road junction near 11,150'. The Pearl Pass road starts on the left and FR 102 continues to the right - Photo #1. Stay right and continue for 2 miles up the road (Photo #2, Photo #3 and Photo #4) to 12,600' near the Montezuma Mine area. Continue on the road (Photo #5) for another 1/2 mile to the end at 12,800' before a small basin - Photo #6.
You must now ascend a headwall to the southwest. When covered with snow, the easiest way to climb it is to traverse across the left side of the basin and then angle toward the middle of the upper slope. Some climbers choose to climb the right side, but it's slightly steeper. Photo #7 and Photo #8 are closer looks at the area. Climb 500' up the headwall to reach the upper basin (13,400') between Castle Peak and Conundrum Peak - Photo #9 and Photo #10. Taken from the east side of the basin, Photo #11 is another look at the area.
Your next goal is to ascend a steep slope that leads to the Castle-Conundrum saddle, seen in Photo #11. The slope holds snow through much of the summer. Hike over to the west side of the basin (Photo #12) and traverse on rock and/or snow to reach the snow slope under the saddle - Photo #13. This slope is the crux of the route and, in late summer, you may encounter 50 to 150 feet of dirt and loose rock above the snow. Above 13,600', turn right and climb directly toward the saddle - Photo #14. Taken from the saddle, Photo #15 looks over the upper basin.
From the saddle (13,800'), turn left and hike southeast along the ridge (Photo #16) on a light trail. Bypass some rock outcroppings on the right to reach steeper terrain near 13,900' - Photo #17. As you approach 14,000' (Photo #18), the rock becomes much more loose and you may have to search for the "trail." Pass another rock outcropping (Photo #19 and Photo #20) on the right to reach slightly easier terrain above 14,100' - Photo #21. Continue winding up through loose rock to reach the summit - Photo #22.
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.