Jenny Lake, formed by glaciers little more than 10,000 years ago, is one of the most popular spots in Grand Teton National Park. And there's a reason. Not only is Jenny Lake the starting point of many Teton trails, it sits at the feet of the park's tallest peaks. What's more, Jenny Lake is great place to canoe and kayak. And while the lake's cold water is likely to put off even the most enthusiastic swimmers, few kids will forego the opportunity to skip rocks and dip their toes.