About 30 miles south of Washington D.C., on the Maryland side of the Potomac River, lies a curious collection of lozenge-shaped islands, the remains of a mighty fleet of wooden steamships built hurriedly during World War I and made obsolete by the end of the war. The unused ships became the center of a political scandal, “the grandest white elephant” ever built, and for decades the government and various salvage companies dithered over what to do with them. Eventually nature herself decided the question: The sunken hulls had consolidated and enriched the sediment in which they lay, creating a valuable new ecosystem. So the armada remains where it is, the largest collection of wrecked ships in the Western Hemisphere.

(Thanks, Craig.)