Skylab II was a space station concept proposed by NASA in the early 2010s, to serve as an outpost in lunar orbit and an evolutionary step towards a Mars transfer vehicle. Like the original Skylab, it would've been built around a modified propellant tank as a dry-workshop, except in this case an SLS hydrogen tank would be used instead of S-IVB. Several configurations with various combinations of docking ports, service modules, and unpressurized truss sections were studied.
Recommended for use with CPS Block 2 https://www.cgtrader.com/3d-models/vehicle/sci-fi/nasa-cryogenic-propulsion-stage-block-2 , Orion https://www.cgtrader.com/3d-models/vehicle/sci-fi/orion-mpcv-spacecraft and the Space Launch System https://www.cgtrader.com/3d-models/vehicle/sci-fi/space-launch-system