Find the geometric centerpoint

[LilleLars]

I have a shapefile, with a map of a country.

And I need to find the geometric centerpoint. Ex if I got Australia on a papir and cut i out. I should be able to put the papir on a neadle, and it should balance. I need to find that point.

Do somebody know how to do that?

Lars

[GuZzO]

fTools provides a tool to extract centroids, that's what you need.
However, i tried to extract centroids from differents layers with QGis and Arcview and there are significant differences between thos 2 processes.