Florence's cathedral dome stays standing because its four million bricks are laid in interlocking spirals

Filippo Brunelleschi completed the Florence Cathedral dome in 1436 by employing a revolutionary herringbone brick pattern that allowed the structure to support itself without wooden scaffolding. The four million bricks are laid in interlocking spirals, creating a self-reinforcing weave that prevents radial slippage even as the walls cantilever at 45-degree angles. This method ensured the dome remained stable throughout the decades-long building process.