Round Lake is a 55-acre body of water located four miles southwest of Sagle in Bonner County, Idaho. It is the prime feature of Round Lake State Park and has 1.2 miles of shoreline. The maximum water depth is 34 feet. The lakeshore and watershed are heavily forested and undeveloped. The shoreline is undeveloped except for the public swimming beach at th…Round Lake is a 55-acre body of water located four miles southwest of Sagle in Bonner County, Idaho. It is the prime feature of Round Lake State Park and has 1.2 miles of shoreline. The maximum water depth is 34 feet. The lakeshore and watershed are heavily forested and undeveloped. The shoreline is undeveloped except for the public swimming beach at the state park.