The Astrodome is most significant in the history of sports stadiums for being the the world’s largest self-supporting dome at the time of its completion in 1965. The difficulty in getting natural light into the stadium led to the development of Astroturf, an artificial replacement for grass. In the early 1960s, ex-Houston mayor Judge Roy Hofheinz proposed the construction of a fully air-conditioned indoor stadium in order to bring baseball to Texas. In 1965, the proposal became a reality when the 18-story high, 9-level domed stadium opened to the public. The building’s enormous steel and concrete exterior and 660-foot-wide circular roof quickly became a symbol of the developing Houston area.