  We propose a consistent setup for the holographic dual of the strongly
coupled large-Nc N=4 super Yang-Mills theory plasma which undergoes the Bjorken
flow relevant to the quark-gluon plasma at BNL Relativistic Heavy Ion Collider
and CERN LHC. The dual geometry is constructed order by order in a well-defined
late-time expansion. The transport coefficients are determined by the
regularity of the geometry. We prove, for the first time, that the dual
geometry has an apparent horizon hence an event horizon, which covers a
singularity at the origin. Further we prove that the dual geometry is regular
to all orders in the late-time expansion under an appropriate choice of the
transport coefficients. This choice is also shown to be unique. Our model
serves as a concrete well-defined example of a time-dependent AdS/CFT dual.
