dome 9
In dome 9 ribs connect the midpoints of the opposite sides, marking a smaller, diagonally placed square. Ribs parallel to the sides of the basic square intersect the midpoints of this 2nd square.
They mark a third square a the base for a 2nd dome whose ribs coincide on the plan with the diagonals of the basic square.
![foto: [url=https://www.flickr.com/photos/100759833@N05/albums/72157649417564427]Santiago Lopez-Pastor[/url]](https://www.geogebra.org/resource/krnm8fzf/ldoEzWMsdAjvVioy/material-krnm8fzf.png)
In the applet below you can see how such a configuration looks like in 3D.