  We explore a mechanism to obtain the observational small value for the
4-dimensional vacuum energy through an exponential warp-factor suppression.
Intriguingly the required suppression scale relates directly to the GUT scale.
We demonstrate the mechanism explicitly in a 5-dimensional brane-world setup
with warped geometry. Upon lifting the setup to 10-dimensional IIB
string-theory, the relevance of the GUT scale becomes clear as the IIB
string-theory description, which is based on D3-brane stacks, gives rise to a
spontaneously broken SU(5) supersymmetric GUT theory with low-energy MSSM
spectrum and Higgs doublet-triplet splitting.
