Dimension 2, put 4 circles radius 1 at (1, 1), (-1, 1), (1, -1), (-1, -1). In the centre, put the largest circle you can. Then from the outside, you can't "touch" the inner circle.
Dimension 3, put 8 spheres radius 1 at (1, 1, 1), ...
Then from the outside you can touch the inner sphere (and it's a bit bigger).
Once you get to a certain dimension (10 IIRC), the inner sphere is no longer in the convex hull of the outer spheres, it is "poking out" of the arrangement.