Nearly six centuries after it was completed, the dome of Santa Maria del Fiore cathedral in Florence — a cathedral known around the world simply as il Duomo (The Dome) — remains that city’s icon and greatest pride. Built without flying buttresses or freestanding scaffolding, using experimental methods that many contemporaries believed would surely fail, the 150-foot-wide (46-meter-wide) dome effectively ignited the creative explosion known as the Renaissance. Until now, experts have never been able to figure out exactly how the Dome’s s creator — Filippo Brunelleschi, a homely, hot-tempered goldsmith with no serious architectural training — actually pulled it off. In a fascinating new special set to air this Wednesday, February 12, 2014 at 9pm, National Geographic and NOVA team up to bring us The Great Cathedral Mystery, and what many are speculating is the long lost secret behind the Dome’s creation. You can learn more by watching the preview above, and a briefing below.