As I descended a spiral of stone steps in a medieval Scottish building, I didn’t pay attention to the fact that, coming down, the metal handrail was on the left and the stairs curved to the right.

Later, I read that it was one of only four right-turn spiral staircases in Edinburgh, the capital of Scotland; most of them turn left. It was “a deliberate design choice to accommodate right-handed swordsmen,” an information sheet in the John Knox House said. “In the event of an attack, defenders descending the stairs would have their sword arm free to fend off assailants coming up.”

Apparently there were no sword fights in the four-story house, built in 1470 and associated in the 1500s with John Knox, the fiery leader of the Protestant Reformation in Scotland. But his controversial life and wo

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