  In this paper we construct a stringy embedding of the dark bubble model of an
expanding 4D cosmology with the help of branes rotating in extra dimensions.
The universe rides a bubble which has nucleated in an unstable higher
dimensional background. Our construction is therefore a string theoretical
realization of Vilenkin's quantum cosmology. While the cosmological constant
vanishes at lowest order, loop corrections predicted by the Weak Gravity
Conjecture can induce a phenomenologically viable value. The model predicts the
existence of large extra dimensions compatible with observational constraints,
and we note a possible connection with the dark dimension proposal.
