As of 2013, I've visited 7 current stadiums:

Seattle (Safeco Field)

San Francisco (AT&T Park)

Oakland (when venue was called Oakland-Alameda County Stadium)

Denver (Coors Field)

Chicago (Wrigley Field)

Toronto (when venue was called the SkyDome)

New York (CitiField)

In addition,

Chicago (Comiskey Park)

Milwaukee (County Stadium)

Cincinnati (Riverfront Stadium)

New York (Shea Stadium and [Old]…