  It is argued that every Calabi-Yau manifold $X$ with a mirror $Y$ admits a
family of supersymmetric toroidal 3-cycles. Moreover the moduli space of such
cycles together with their flat connections is precisely the space $Y$. The
mirror transformation is equivalent to T-duality on the 3-cycles. The geometry
of moduli space is addressed in a general framework. Several examples are
discussed.
