The harder dolomite forms much of the rock of the escarpment cliffs along Bruce Peninsula National Park's Georgian Bay shoreline. At Niagara Falls, the dolomite "caprock" is more resistant to erosion than the rock below it, creating the sculptured cliffs for which the area is famous. Since the last Ice Age, water levels in the region have undergone great changes. Softer limestone has been eroded away by water action, leaving magnificent overhanging cliffs at various points along the shore. These are the big attraction of the Cyprus Lake trails. Where erosion has cut more deeply, caves have been formed, such as the famed "Grotto" on the shore between the Marr Lake and Georgian Bay Trails. Great blocks of dolomite, undercut by wave action, have tumbled from the cliffs above and can be clearly seen below the surface of the deep, clean waters of Georgian Bay.