I've been to several major league stadiums, most are no longer in use:
Fenway, the original Yankee Stadium (before remodeling), Shea, Municipal Stadium in Cleveland, Exhibition Stadium in Toronto, Comiskey Park (I and II), Wrigley, Royals Stadium, Busch Stadium (the one the Sox won the 2004 World Series in), the Astrodome, County Stadium in Milwaukee (saw Rice's 300th homer there).