The internet is telling me that the walls at Tiger Stadium were moved back in 1955, taking out the flagpole and the hill. If I remember correctly when they built the current park in Houston there was a hill in centerfield (not sure about the flagpole)
Comerica had the flagpole in play when it was first constructed. I think it was during the 2001 season I saw Sammy Sosa hit a bomb in that direction, he did the patented home run hop then watch the ball fall harmlessly into the CF's glove ( I can't remember who)
One of my favorite early Comerica moments