  We present a short review of the group-geometric approach to supergravity
theories, from the point of view of recent developments. The central idea is
the unification of usual diffeomorphisms, gauge symmetries and supersymmetries
into superdiffeomorphisms in a supergroup manifold. The example of $N=1$
supergravity in $d=4$ is discussed in detail, and used to illustrate all the
steps in the construction of a group manifold action. In the Appendices we
summarize basic notions of group manifold geometry, and of integration on
supermanifolds.
