
01 · Brunelleschi's dome
Two shells inside the dome
Another dome lies beneath the red tiles.
When Brunelleschi took on the job, the cathedral already had a huge octagonal opening waiting to be covered. He built an inner and an outer shell, linked by ribs, with passages between them. The bricks did not simply run in horizontal courses: upright bricks broke across them in a herringbone pattern, helping the work stay stable during construction. People climbing the dome today enter that gap. What is invisible from the square becomes stairs underfoot and curved masonry overhead.
Source: en.wikipedia.org

