Edifice Complex

The Duomo of Florence, a polychrome marble foundation for the impressive dome of the Renaissance.

That red dome is an enormous pile of four million bricks, weighing 37,000 tons, and is still the largest masonry dome in the world. It was erected in 1420-1436, without scaffolding or wood supporting beams. Critics argued vehemently that the design was impossible and would collapse onto the impressive structures below.

“Brunelleschi’s solutions were ingenious and unprecedented: the distinctive octagonal design of the double-walled dome, resting on a drum and not on the roof itself, allowed for the entire dome to be built without the need for scaffolding from the ground. But, because the dome rested on a drum with no external buttresses supporting it, there could be no lateral thrusts at the base of the dome. To ensure this, Brunelleschi used horizontal tension chains of wood and iron set at the base of the dome.
The ability to transcribe a circle on a cone face within the innermost double-shelled wall makes the self-sustaining “horizontal” arch construction possible, since geometrically, a circular plan is needed for such an erection.” – from Wikipedia

He even had to invent new hoisting machines to get the heavy rocks up there and a gearbox pulley to lift weight up and then slightly down into place, without a reversal of horse power.

(I must have had a strangely steady hand as this composite of three shots at different exposures came out sharp, and I was not resting the camera on anything)