Traveling east, Highway 21 skirts the southern edge of the massive 43,000-acre Necedah National Wildlife Refuge, home to a fledgling whooping crane population. Four miles east of Necedah, the bridge across the Wisconsin River marks the center of a favorite tourism destination that includes Petenwell Lake to the north and Castle Rock Lake to the south. They are the second- and fourth-largest lakes in the state; both formed by dams on the river.