Peyto Lake should be considered in any 'best lake in the world' list. The water is strikingly turquoise and the rustic scenery sets it apart from Lake Lousie a bit, as there's no fancy hotel along its banks.
Even if you don't time things perfectly, however, the glacier-fed lake still offers colorful water beyond its peak season.
Named for Billy Peyto, a famed early trapper and trail guide to the area, Peyto Lake is easily accessible from the Columbia Icefields Parkway. If you come in the winter, you'll miss out on the beautful turquoise color of the lake, but its surrounding countryside is excellent for snowshoeing.