Hannes Grobe · CC BY-SA 2.5

Hundertwasser built a career on refusing the straight line, arguing that rigid grids in architecture were a kind of violence against human individuality, and put that conviction into buildings rather than manifestos alone. His best-known work, the Hundertwasserhaus apartment complex in Vienna, wraps irregular, planted, brightly colored forms around ordinary housing and remains one of the city's most visited sites. He was also an early and outspoken environmentalist, integrating trees and vegetation directly into his designs decades before green architecture became a movement.