  Cosmological simulations are crucial tools in studying the Universe, but they
typically do not directly match real observed structures. Constrained
cosmological simulations, on the other hand, are designed to match the observed
distribution of galaxies. Here we present constrained simulations based on
spectroscopic surveys at a redshift of z~2.3, corresponding to an epoch of
nearly 11 Gyrs ago. This allows us to 'fast-forward' the simulation to our
present-day and study the evolution of observed cosmic structures
self-consistently. We confirm that several previously-reported protoclusters
will evolve into massive galaxy clusters by our present epoch, including the
'Hyperion' structure that we predict will collapse into a giant filamentary
supercluster spanning 100 Megaparsecs. We also discover previously unknown
protoclusters, with lower final masses than typically detectable by other
methods, that nearly double the number of known protoclusters within this
volume. Constrained simulations, applied to future high-redshift datasets,
represents a unique opportunity for studying early structure formation and
matching galaxy properties between high and low redshifts.
