Taos Pueblo
Credit: Getty Images

America's first apartment building is roughly 1,000 years old. The Taos Pueblo was reported to be six stories high when conquistadors first arrived at the New Mexican complex's thick adobe walls in 1540. The complex, which regulates heat naturally and is easily navigable so long as the ladders connecting each level are in place, is still one of the most influential piece of architecture in America largely because it is the perfect epitome of southwestern simplicity. There is no excess ornamentation, only rounded walls that give a lasting impression of geologic permanence – as though the whole thing is nothing more than another mesa. Despite being made of branches, grass, plaster, and mud, it shows no sign of crumbling with age.