Thank you all for your comments...
@ Twinis
I like to work with mirrors, as your scene show you can create great effects with it.
@ DOGGOD
The mirror floor plan is a very simple set up.
I used a glass floor as first step and then I used 8 mirror-wall elements to build the mirror-room
In Daz3d it looks like this:
topview:

frontview:

The glass floor you'll find here: https://zonegfx.com/dms-mirror-talk/
The mirror-wall elements you'll find here: https://zonegfx.com/i13-yoga-studio-bundle/