[When it first opened in 1965, Houston's Astrodome was called the "Eight Wonder of the World." It was the world's first domed, indoor stadium and boasted air conditioning for Astros and Oilers games. Closed in 1996, it was named to the National Register of Historic Places earlier this year, though it's still in danger of being demolished after voters rejected a bond referendum that would've authorized spending more than $200 million to repurpose the structure. Photo: Michael Nitzani.]