  We investigate the emergence of supersymmetric negative-vacuum-energy ground
states in four dimensions. First, we rely on the analysis of the effective
superpotential, which depends on the background fluxes of the internal
manifold, or equivalently has its origin in the underlying gauged supergravity.
Four-dimensional, supersymmetric anti-de Sitter vacua with all moduli
stabilized appear when appropriate Ramond and Neveu--Schwarz fluxes are
introduced in IIA. Geometric fluxes are not necessary. Then the whole setup is
analyzed from the perspective of the sources, namely D/NS-branes or
Kaluza--Klein monopoles. Orientifold planes are also required for tadpole
cancellation. The solutions found in four dimensions correspond to domain walls
interpolating between AdS4 and flat spacetime. The various consistency
conditions (equations of motion, Bianchi identities and tadpole cancellation
conditions) are always satisfied, albeit with source terms. We also speculate
on the possibility of assigning (formal) entropies to AdS4 flux vacua via the
corresponding dual brane systems.
