We drove over to Old Faithful just in time to see the big geyser erupt. We had lunch in the inn at Old Faithful--it was the first time I wore my Penn State shirt and we met a couple from Pittsburgh who had just been to the Glacier NP.
On the way back to the cabin, we stopped to see the Grand Prismatic Spring -- a crust of heat-loving microbes formed on top of the pool creates a rainbow of colors and smells of sulfer. Signs by the boardwalk threatened us, but it looked like a hoofed animal had walked across the crust--don' know if it fell in.