  Simulations of an isolated Milky Way-like galaxy, in which supernovae power a
galactic fountain, reproduce the observed velocity and 21cm brightness
statistics of galactic neutral hydrogen (HI). The simulated galaxy consists of
a thin HI disk, similar in extent and brightness to that observed in the Milky
Way, and extra-planar neutral gas at a range of velocities due to the galactic
fountain. Mock observations of the neutral gas resemble the HI flux
measurements from the Leiden-Argentine-Bonn (LAB) HI, survey, including a
high-velocity tail which matches well with observations of high-velocity
clouds. The simulated high-velocity clouds are typically found close to the
galactic disk, with a typical line-of-sight distance of 13kpc from observers on
the solar circle. The fountain efficiently cycles matter from the centre of the
galaxy to its outskirts at a rate of around 0.5 M_sun/yr
