$36

Opened in 1965 and closed in 2008, Houston's Astrodome (so called to honor NASA's newly opened Manned Spacecraft Center) saw nearly 50 years of Astros action, including 7 division titles and one pennant win.  The dome itself is not without milestones of its own--it popularized the use of AstroTurf and housed 25,000 evacuees in 2005 after Hurricane Katrina.  Pay homage.