Unlike the fairly simple systems in Ingress and Pokemon Go, there are a number of different building types in Harry Potter: Wizards Unite. Each offers a united set of activities for you to perform and earn rewards from. The largest of these buildings are called Fortresses, and contained within these super tall structures are Wizarding Challenges.

: https://www.imore.com/how-complete-wizarding-challenges-harry-potter-wizards-unite