What is gtkmm default font and size?

[John Taber <jtaber johntaber net>]

When a gtkmm program (and any gtk program for that matter) runs under Gnome, 
the fonts are nice, but when it is run under KDE, the fonts are terrible - 
what font and size does gtkmm default to?  I would assume this is best 
addressed from the user settings (in KDE the Control Center allows user to 
select font and size for various types).