We study the gravitational description of conformal half-BPS domain wall operators in N=4 SYM, which are described by defect CFT's. These defect CFT's arise in the low energy limit of a Hanany-Witten like brane setup and are described in a probe brane approximation by a Karch-Randall brane configuration. The gravitational backreaction takes the five-branes in AdS_5xS^5 through a geometric transition and turns them into appropriate fluxes which are supported on non-trivial three-spheres.