Hello, I want to do sacred geometry constructions with Inkscape.

As such, I want to be able to place circles with respect to other circles based on the center of a circle. So I want a small cross hatch in the center of the circle so I can place things exactly.

What? Have you tried using the align menu? ctrl+shift+A. (Fixed, thanks kelan!) Hover over the icons to read what they do. Play around with it, you'll get the hang of it.

Just remember that sometimes you'll need to group some objects for them to be treated correctly.

Oh, and for the circle thing, press crtl+D to duplicate the circle (on top of other one) hold shift+alt (or something like that ) and you can shrink the circle without moving the center. Its a good idea to use the align button afterwards, just to make sure.

Could you use guides for the crosshair mark?
I'm not familiar with sacred geometry, but I like to make mandalas (symetrical designs inside a circle) and I frequently use guides to mark the center of circles.

Also, you may find the Snap feature to be helpful. I recently made a mandala which had 4 identically sized circles inside. After putting the guides to mark the center, I enabled Snapping of bounding boxes to guides. This made certain that the circles fit perfectly, one in each quadrant of the circle. I'm not quite sure, off the top of my head, how it would be done for more than 4 circles. But with your familiarity with geometry, you may be able to easily work it out.

I hope this is helpful

SureWhyNot wrote:What? Have you tried using the align menu? ctrl+shift+L.

I believe SureWhyNot meant Ctrl-Shift-A for the Align and Distribute dialog. Ctrl-Shift-L opens the Layers dialog.