It wouldn’t be summer without a trip to the pool—but those harsh chemicals can be a real turnoff. These days, eco-conscious and design-savvy homeowners are increasingly adopting an unorthodox means of pool filtration: plant life. Aquatic plants and naturally occurring bacteria not only filter the water, they also contribute to the landscaping. Yes, natural pools require more planning than the standard-issue variety, but you can—with a little know-how and not an overwhelming amount of trouble—build a fairly self-sufficient swimming pool (or give an earth-friendly upgrade to your existing pool). Besides being less costly to maintain, natural pools come with an additional bonus: They don't have to be shut down come winter. In fact, if temperatures drop low enough, your pool can double as an ice rink. So come take a tour of some of our favorite natural swimming pools, each more inviting than the next.