Grab tickets to watch a game at Linzer Stadium. If there's nothing on while you're there, you might like to check if there's a guided tour of the grounds.
You'll soon realize why this sporting facility is on the must-see list of many travelers to Froschberg. After you've paid the entry fee, wander inside and stick around a while. After more things to keep you busy close to Linzer Stadium? Check out Linz Castle Museum, Lentos Art Museum and St. Martins Church.