The KIO Towers at Puerta Europa are twin office buildings flanking the Paseo de la Castellana, Madrid’s most important boulevard. Designed by American architects Philip Johnson and John Burgee, each building is 115 m tall with an inclination of 15°, making them the first inclined skyscrapers in the world. Due to financial difficulties, construction for the towers was rather slow and lasted from 1989 until 1996, with long-lasting interruptions in the works. (PG)