Leuven is a low-key family destination: no theme park, but a large provincial park, a water playground and free forest on three sides.
Provinciedomein Kessel-Lo
A big provincial recreation park on Beemdenstraat, free to enter, with playgrounds, pedal and rowing boats, mini-golf, a roller-skating rink and a traffic park for ages 4–12 in the Easter and summer holidays. Attractions run 1 April to 30 September; the paddling pond is closed pending a new swimming facility.
Sluispark water playground
A free park on the Dijle in the Vaartkom, between Sluisstraat and Burchtstraat, with a water play area and broad steps down to the water that work as seating. Handy if you are staying near the docks and need to burn an hour before dinner.
Zoetwaterpark, Oud-Heverlee
A municipal play-and-sport park at Gemeentestraat 10, just south of Leuven: skatepark, pumptrack (helmet required), mini-golf and an open pavilion, free and open sunrise to sunset. Sports equipment is lent free at Easter, on spring and autumn weekends and through the summer holidays.
M Leuven
The city art museum at Leopold Vanderkelenstraat 28, free for everyone aged 18 and under and €6 for 19–25s, €16 full price. Open 11:00–18:00, to 22:00 on Thursday, closed Wednesday; family trails and HoloLens tours run with St Peter's Church next door.
Park Abbey grounds
A 12th-century Norbertine abbey at Abdij van Park 6 in Heverlee, with fish ponds, gatehouse and farm buildings. The abbey park is open every day and free to walk; reception, shop and the PARCUM museum run Tuesday to Sunday, and there is a mouse-guided tour for 6–10s.