  We consider how the energy can be stored in the boundary of spacetime, in
particular in a spherical bubble that can be made by a quantum gravitational
process. Our calculation is performed within the framework of classical
Einstein gravity by identifying the Gibbons-Hawking-York term as the membrane
action. We show that the energy of the bubble can be given consistently with
the Schwarzschild metric. The solution of the consistency condition suggests
positive membrane tension, which explains why we do not observe such
topological defects in ordinary experiences and also gives a mechanism for
suppressing the spacetime with boundary in a dynamical way.
