Yellowstone is America's and the world's oldest national park, established in 1872. With all of its wildlife and thermal features, natural rock spans would not be on a typical visitor's itinerary. But, we're spanophiles, so, of course, we try to pay attention to the possibility of natural rock spans wherever we go. As it happens, we know of three natural rock spans in Yellowstone National Park: one unnamed arch in the Firehole River Canyon, Grotto Geyser, and the Yellowstone Natural Bridge.

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