  We study localization of gravity in flat space in superstring theory. We find
that an induced Einstein-Hilbert term can be generated only in four dimensions,
when the bulk is a non-compact Calabi-Yau threefold with non-vanishing Euler
number. The origin of this term is traced to R^4 couplings in ten dimensions.
Moreover, its size can be made much larger than the ten-dimensional
gravitational Planck scale by tuning the string coupling to be very small or
the Euler number to be very large. We also study the width of the localization
and discuss the problems for constructing realistic string models with no
compact extra dimensions.
