  New boundary conditions for asymptotically flat spacetimes are given at
spatial infinity. These boundary conditions are invariant under the BMS group,
which acts non trivially. The boundary conditions fulfill all standard
consistency requirements: (i) they make the symplectic form finite; (ii) they
contain the Schwarzchild solution, the Kerr solution and their Poincar\'e
transforms, (iii) they make the Hamiltonian generators of the asymptotic
symmetries integrable and well-defined (finite). The boundary conditions differ
from the ones given earlier in the literature in the choice of the parity
conditions. It is this different choice of parity conditions that makes the
action of the BMS group non trivial. Our approach is purely Hamiltonian and
off-shell throughout.
