  We investigate a family of SU(3)$\times$U(1)$\times$U(1)-invariant
holographic flows and Janus solutions obtained from gauged $\mathcal{N}=8$
supergravity in four dimensions. We give complete details of how to use the
uplift formulae to obtain the corresponding solutions in M theory. While the
flow solutions appear to be singular from the four-dimensional perspective, we
find that the eleven-dimensional solutions are much better behaved and give
rise to interesting new classes of compactification geometries that are smooth,
up to orbifolds, in the infra-red limit. Our solutions involve new phases in
which M2 branes polarize partially or even completely into M5 branes. We derive
the eleven-dimensional supersymmetries and show that the eleven-dimensional
equations of motion and BPS equations are indeed satisfied as a consequence of
their four-dimensional counterparts. Apart from elucidating a whole new class
of eleven-dimensional Janus and flow solutions, our work provides extensive and
highly non-trivial tests of the recently-derived uplift formulae.
