Downhilling at Keystone

Keystone runs a lift during the summer to carry bikes to the top of the mountain. In about 10 minutes you gain 2700 vertical feet and the trails to the base are almost all downhill. Today was my first experience with lift serviced downhill mountain biking. It was a lot of fun but utterly exhausting. I did 5 laps on the chair and ended up riding over 30 miles down all sorts of trails. There are good variety of trails down the mountain (trail map here). Trails are marked with familiar green, blue, black and double black ratings. I started out on greens with names like Girl Scouts and Easy Street. These single track trails were technically easy, but still physically demanding. It was a long way down no matter which way you went. It generally took me 45 minutes to an hour to get down. (It takes 5-10 minutes to ski the same distance in the winter). The trails wind their way down the mountains crossing ski runs and traveling through the forest. Trails like Let it Ride seemed to go on forever. If you took the green trails all the way down it was about 8 miles top to bottom.
I eventually worked my way up to some blues which were not much more difficult than the greens. Maybe a little steeper in places. Then I decided to try the black diamond trail "Cowboy Up." It was one of the most technical trails I have ever ridden. There were some really steep sections and a few substantial log drops. I wasn't too comfortable with an unfamiliar bike with no clipless pedals. I was heading down through a nasty rock garden when I got to a section which looked too tough to ride. I saw some people coming up behind me so I scooted off the trail to watch them come down. The first guy who looked like he knew what he was doing and had the right bike and the gear to be riding the trail bailed on the section that I stopped for. He went over the bars and landed pretty hard. I walked that section after seeing that. I decided the blacks were a little out of my league today. I can't even imagine what the double blacks were like.
At the end of the day I was exhausted. Riding 30+ miles on rough trails does a number on your body, even on a plush full suspension bike. My arms were especially tired. Overall it was a great day. Not having to ride uphill is kind of weird, but it really maximizes excitement. Riding uphill at Keystone would be brutal because of the elevation gain.