  We use the AdS/CFT duality to study the special point on the Coulomb branch
of ${\cal N}=4$ SU(N) gauge theory which corresponds to a spherically symmetric
shell of D3-branes. This point is of interest both because the spacetime region
inside the shell is flat, and because this configuration gives a very simple
example of the transition between D-branes in the perturbative string regime
and the non-perturbative regime of black holes. We discuss how this geometry is
described in the dual gauge theory, through its effect on the two-point
functions and Wilson loops. In the calculation of the two-point function, we
stress the importance of absorption by the branes.
