Eldorado is a fun climb, all on relatively low-angle snow, with a classic knife-edge summit ridge finish. The Sibley Creek approach adds some serious scrambling on a ridge approach to a camp, and up/down some rock gullies and traversing around the Triad on the approach.
A nice lead on a Mazama climb by Keith Dubanevich. I got to assist because the original assistant had to retreat early with a climber who couldn't stomach the exposure on the approach ridge. I must be sick, I thought it was loads of fun - both in the fog and in the sun! Alternating exposed scrambling and waltzing through ridgetop flowery meadows.
Routefinding too - we had folks in the middle of the party wander off the route! And we picked a wrong exit guly from the first valley on the way in - the correct gully is only 30 feet down and around a blind corner; only 3rd class instead of 5th. As I was preparing to rap the 5th-class gully, leading on the way out, Keith comes up and smells out the right gully. Good leader instincts!
The basecamp is a definite top-five - a rocky/grassy knoll overlooking Sibley Creek and Marble Creek Cirques, just below the western edge of the Triad. It's 50 yards from the top of the gully that drops off the ridge to the NE to start the climb-day appoach, and a good stopping place so you don't have to do this gully in full packs.
Oh, did I mention, it ranied - hard - as we arrived at the Mablemount R/S, so we got to wait there and watch movies for a couple of hours...Welcome to the North Cascades! The topo shows the precise route, as well as I can plot it.
Eldorado/Sibley Creek route map
Eldorado/Sibley Creek route map TOPO! file
Steve Marston's Eldorado photos