The watch tower is on the highest part of the rim of the Sand Mountain cinder cone, and the intended trail runs from just above the old trail head directly up the back side of that ridge to the tower. We took a "wrong" turn (actually, just went straight instead of making the "correct" turn), and followed the old trail, which provides more interesting geology, (Sorry, no pictures; I was awfully tired at that point, but you can see some of the welded layers on the slope to the left of the tower.) and a more gradual climb. I know they're trying to be protective of the vegetation in the area, but I would recommend others who make this climb make the same mistake. The walk down was awfully steep, and I would not have wanted to climb up that way.
In related news, Hollie's husband has posted his own account, with photos and maps, of our outing last Sunday.