Essentially achieved this with the tunnel - I have a much stronger understanding of holes and so on. Not clear that I desperatly need to inset any buildings, but I certainly could if I wanted too. Would it be interesting to have a doorway off the tunnel??
Practice embedding a building into the landscape a little more so it’s easy to enter (beware of this a bit though because it will involve terraforming and then I’ll have to rebumpify the landscape?) Platform that switches off the sun (back on when you get off)