Updated Sketchup models (with stairs)

Below Ground - "Swim"
To do:
1. Alter top of stairs to be only a few cm above water
2. Extend terrain to make space for the Above Ground model

Above Ground: Plumbing
This is a very rough model showing my changing concept. Major changes will be needed:
1. Make structural support pipes frame a gallery space
2. Make pipes curve around the main room
3. Combine with Below Ground model

EDIT:

This image shows how the two models are combined. The lower (under water) staircase is much wider than the upper one, suggesting to an occupant that one can walk on either side of the upper staircase towards the area under tha large pipe. This area will be roughly walled in by curving pipes, which will support that large pipe above.