Done in Inkscape.
I think what impresses me the most with this picture is the fact that you'e actually made it look three dimensional thanks to the gray curves on the lower half of the picture. Combined with the impressive details on the upper half of the picture, the composition is splendid! I also like how the two largest ovals seems to collide with each other, I see you even emphazised the spot with red outline on the right oval as well, smart choice! Definitely one of my favourites so far.
pretty nice, looks like i should check out Inkscape.