Cirques are amphitheater-shaped valleys generally formed by alpine glacier action. Lakes and ponds in the scooped out depressions of some cirques are called tarns. I search for tarns on maps and on aerial photos. They don't always show up on older maps... many were covered in ice until the mid-1900s. The lip or sill, the low area at the opening of a cirque, is sometimes a good picnic site with 360 degree views. Visiting most tarns in the park is a significant logistical and exertion challenge. Photographer: Bill Eichenlaub