From Breckenridge, drive 8 miles south on Colorado 9. On a sharp corner of Colorado 9, turn west onto the 850 road (Blue Lakes road). It is 2 miles to the trailhead below the dam. Continue on Blue Lakes road as it climbs west. After 1.2 miles, keep right. After 1.4 miles, keep right again. By early June, the road is usually open to the dam. If not, drive as far as possible and hike the remainder of the road. There is a large parking area below the dam.
The South Gully (aka Cristo Couloir) is recommended for snow climbing/skiing but is also used as a descent after climbing the west ridge route. Photo #1, Photo #2 and Photo #3 show most of the route seen from the southeast. From the parking area, hike up a small slope that leads up to the top of the dam. From the pavement on the north end of the dam, turn right and start up the slope. Photo #4, Photo #5, Photo #6 and Photo #7 show the route seen from the top of the dam. Your immediate goal is to ascend about 200' through rock and bushes to get to an open area that is east of the base of the gully. Once you are in the open area, walk on easier terrain as you angle up to the left (northwest) toward the base of the gully - Photo #8. You can also cut directly left (west) and cross the hillside until you hit the gully.
When you reach the lower portion of the gully, begin climbing the snow (Photo #9) or hike up along the side on rocks and scree. If you choose to stay away from the snow, it is best to climb the left (west) side. Climb along the gully (Photo #10) as it ascends toward the summit. Near 13,000', the gully begins to widen and there may be large rocks in the center.
Near 13,400', the gully becomes wider and a bit more steep - Photo #11 and Photo #12. If you are snow climbing, the most exciting route may be straight up the center of the gully. Taken between 13,500' and 13,800', Photo #13, Photo #14, Photo #15 and Photo #16 show the steep, upper portions of the gully. If you are still trying to avoid the snow, continue on the left side. Photo #17 and Photo #18 show the last few hundred feet below the summit. Near 14,000' and with just a short distance remaining in the climb, the slope begins to ease. Photo #19 looks over the top of the gully and Photo #20 looks south from just below the summit. Pick your line and gain the summit - Photo #21.
By late May, the terrain between the top of the gully (~13,900') and the summit may be melted out. Photo #6, Photo #8 and Photo #12 show the gully in prime ski condition. Photo #13 was taken near 13,600' in the center of the gully - you can see the area below where the snow was missing. In some years, the gully has great snow into June. If conditions are right, you may be able to ski down to 12,000', or all the way to the lake. The lower portion of the gully is narrow (more like a trench) but usually holds snow. Photo #22, Photo #23 and Photo #24 were taken during a ski trip.
When the snow is gone, the center of the gully contains loose rock, so it's best to stick to the west edge where you'll find more stable terrain and some trail segments. With snow, crampons, axe and a helmet are recommended.