When Edward Leedskalnin’s fiancée left him at the altar, the Latvian eccentric moved to Florida and started building a castle to win her back. A very, very heavy castle: The structure is made of megalithic stones, mostly coral, each of which weighs several tons.

How he did it is something of a mystery, as the 100-pound artist worked only alone and at night. Some teenagers who glimpsed the construction said that he moved the blocks like hydrogen balloons. Leedskalnin gave no details but spoke of a “perpetual motion holder” and said he knew the secret of the Egyptian pyramids.

Anyway, did it work? Sadly, no. Leedskalnin spent 28 years building his castle, but when his erstwhile fiancée heard about it, she said, “I didn’t want to marry Edward when I was 16, and I don’t want to marry him now.” He died a few years later.