  Horizon Run 5 (HR5) is a cosmological hydrodynamical simulation which
captures the properties of the Universe on a Gpc scale while achieving a
resolution of 1kpc. Inside the simulation box we zoom-in on a high-resolution
cuboid region with a volume of $1049\times119\times127\,{\rm cMpc}^3$.The
sub-grid physics chosen to model galaxy formation includes radiative
heating/cooling, UV background, star formation, supernova feedback, chemical
evolution tracking the enrichment of oxygen and iron, the growth of
supermassive black holes and feedback from active galactic nuclei (AGN) in the
form of a dual jet-heating mode. For this simulation we implemented a hybrid
MPI-OMP version of RAMSES, specifically targeted for modern many-core many
thread parallel architectures. In addition to the traditional simulation
snapshots, light-cone data was generated on the fly. For the post-processing,
we extended the Friends-of-Friend (FoF) algorithm and developed a new galaxy
finder PGalF to analyse the outputs of HR5. The simulation successfully
reproduces observations, such as the cosmic star formation history and
connectivity of galaxy distribution, We identify cosmological structures at a
wide range of scales, from filaments with a length of several cMpc, to voids
with a radius of ~100 cMpc. The simulation also indicates that hydrodynamical
effects on small scales impact galaxy clustering up to very large scales near
and beyond the baryonic acoustic oscillation (BAO) scale. Hence, caution should
be taken when using that scale as a cosmic standard ruler: one needs to
carefully understand the corresponding biases. The simulation is expected to be
an invaluable asset for the interpretation of upcoming deep surveys of the
Universe.
