Based on the Ayria concept of avatar living spaces.

The following text taken from the Ayria link is designed to help you with the placement of the items....

Ayria has five invisible levels of floor nodes so you can build up into the sky using the specially developed building components and furniture pieces. There is a placement grid to assist you that will show you where all the nodes are; just type ‘setgrid’ to show the grid and ‘unsetgrid’ to hide it again.

Building an Ayria living space does take patience as it is not easy moving the components around in 3 dimensions, but practice does make it easier and it is worth it to be able to use your own creativity to build a beautiful space.

This is the Granite arch.