Enceladus is the moon which houses the orbit for the Enceladus Prime station.
Plumes of water escaping from Enceladus' surface, taken by the Cassini probe. ©NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill
Despite not being the closest moon to the Rings, Enceladus was chosen for the near-constant plumes of water providing a dampening effect to the natural radiation levels, making for some of the lowest levels in the Solar System.
The naturally high water content of both the moon as well as Saturn's Rings in general also made for a decently habitable region of space.