  We study geometric characterizations of the Poincar\'{e} inequality in
doubling metric measure spaces in terms of properties of separating sets. Given
a couple of points and a set separating them, such properties are formulated in
terms of several possible notions of energy of the boundary, involving for
instance the perimeter, codimension type Hausdorff measures, capacity,
Minkowski content and approximate modulus of suitable families of curves. We
prove the equivalence within each of these conditions and the $1$-Poincar\'e
inequality.
