Herberstein Castle and Zoo make a substantial day trip east of Graz, combining a historic Styrian castle above the Feistritz gorge with gardens, museum spaces, and a large wildlife park. The official Tierwelt Herberstein site presents it as an animal world with roughly 700 animals, but the appeal is broader than a standard zoo because the castle landscape shapes the visit.
The site works especially well for families, but it is not only for children. Castle courtyards, formal gardens, wooded slopes, and animal enclosures sit close together, so the day alternates between architecture, views, and wildlife. Public transport is possible but awkward; a car makes the trip much easier.