Green Lakes State Park: Fayetteville, New York

Tucked into a scrap of old growth forest in upstate New York are two emerald lakes, and I got to visit one last summer. The brilliant color is because they are extremely deep, glacier-carved potholes filled with ancient water that never mixes (in most lakes, water from the bottom and the surface mix at regular intervals, kicking up sediment). There are only a dozen or so of these meromictic lakes in the U.S., so it is a very special experience. We rented kayaks and go out for a paddle on Green Lake (outside boats aren't allowed in, to protect its unique ecosystem) and spent an hour peering into the depths, marveling at the color, and looking up to spot the osprey.