In the summer of 1518, in the town of Strasbourg (modern-day France), a bizarre phenomenon unfolded. A woman known as Frau Troffea began dancing fervently in the streets, and within days, dozens had joined her. The dancing continued unabated, with more and more people joining in, some reportedly dancing for days without rest. Medical professionals were baffled, and theories ranging from mass hysteria to ergot poisoning (a fungus known to cause hallucinations) have been proposed, yet the true cause remains a mystery.