Stairs:The floating staircase is prevalent in villainous lairs so was an obvious, iconic thing to include. Rather than being truly to scale I wanted a set of steps that could have miniatures placed on them. Foam PVC (sorry to keep banging on about it!) was an easy solution to the relative weakness of the design, being just a central riser with multiple steps. I used 5mm for the riser and 3mm for the steps.
I decided on a 5mm gap between each step. First marking out the riser with the step positions 8mm apart (vertical). The depth varied with each set of steps, depending on how steep I required them. For this set it was 10mm (horizontal). Each step was 40mm wide and 20mm deep. The 5mm gap gives ample room to fit a figure base but means I could use 5mm foamcore spacers. Foamcore was used as if I did mange to superglue it to the staircase it would be easier to remove than foam PVC spacers.

I used a piece of MDF to keep the alignment of the steps true as I superglued each one in place. Once I had figured out the construction it proved straightforward to adapt the design to fit specific sizes for different parts of the table.

Once built they are just about stable enough to stand freely, although mine will be secured to other parts of the scenery. The top step on this one is slightly different to fit the intended location. As you can see a miniature base fits easily into the gaps.
Take a giant step for mankind...