Duomo & Brunelleschi's Dome

In 1418 Florence had a cathedral with a 45 m hole in its roof and no known way to close it. Brunelleschi, a goldsmith with no architectural training, won the job with a scheme he refused to explain: a double-shell dome, stone-and-iron chain hoops to contain the thrust, and bricks laid in a herringbone spiral so each course locked itself in place as it rose into empty air.

He invented the world's first reversing-gear ox hoist to lift the stone, and ran a canteen up in the dome (wine served diluted, one third water) so masons wouldn't waste daylight descending. Masonry done in 16 years. Michelangelo, asked to beat it at St. Peter's, said: 'bigger, yes, but not more beautiful.'

If you climb, you pass between the two shells with the herringbone inches from your face. If you don't, the Opera del Duomo Museum holds Ghiberti's original Gates of Paradise, Michelangelo's late Bandini Pietà, and Brunelleschi's actual hoisting machines: for engineering hearts, possibly better than the Uffizi.