Gustavsvik is a big indoor water park and leisure complex south of central Oerebro. It is not the reason to come to the city, but it is a practical and popular stop if you are travelling with children, especially when the weather turns against castle-and-walking plans.
The complex mixes pools, slides, and tropical-themed play areas with the usual Swedish efficiency. For independent travellers without kids it will probably feel skippable, but families can use it as a half-day pressure valve after museums, Wadkoeping, and the city centre.