Nice clean examples. Welcome to GameDev
Good first models.
Welcome to this site.
That spiral staircase will take some climbing! May be a bit of an issue with health and safety though, all open to falling off at any point.
I thought it is a water drill …
I wondered that at first but there is no way it can do so without being inside a tube. Further the top looks like a walkway rather than any liquid transfer system.
I guess it could be an abandoned drill used to make the holes for the tank legs! Or waiting for use to make the next one.
You were right they are stairs and the top is a walkway to reach the tank.