Some of the same natural forces that once made Yellowstone National Park so scenic also made Island Park similarly beautiful. Island Park sits in the world's largest caldera, 23 miles in diameter, created from a volcano that collapsed in prehistoric times. Now covered in a dense forest of pine and wildflowers, it is popular for hiking and fishing in the summer and cross country skiing and snowmobiling in the winter. The Henry's Fork of the Snake River is world famous for fly fishing, and is curtailed here to form the 7,000 acre Island Park reservoir, popular to both anglers and boaters. The Henry's Fork then winds through the meadows of one of Idaho's most premiere state parks, Harriman State Park