This is a natural arch near Coldwater Peak in the Mount St. Helens National Volcanic Monument. The arch is quite unique with the Boundary Trail passing though the arch. It is located west of Spirit Lake near St Helens Lake and can actually be seen from the Johnson Ridge Visitors Center. The arch was there before the mountain blew but it was obscured with timber. Once the timber was blown away the arch was "discovered" and the new Boundary Trail was constructed to pass through it. A nice hike, about 5 miles from the Johnson Ridge Visitors Center. The mountain in the photo is Mt Adams.