If you look closely along left-center field you can see the "Billy Goat Trail" up to deep center field. Yes, deep center field was in play, which means outfielders had to run up there to field well-struck balls to center. Amazing.
EJ Fagan, who was interviewed in David Temple's podcast, posted this article that gives more pictures, more anecdotes, and news accounts of what it was like to play there. It's a great article, so please give it a look.