We went to the Stanford Sierra Camp on Fallen Leaf Lake. The camp is run by the alumni association, and has programs for children ages nine months and up. The counselors are all Stanford undergraduates. The week we went (the last of the season) was geared towards smaller children- an incredible number of kids running (and screaming) in all directions. We took one modest hike into the neighboring Desolation Wilderness, and went rowing and kayaking. None of us quite had to courage to swim; Fallen Leaf Lake is four hundred feet deep in places and stays quite cold all year round.
