  We present a new determination of the surface brightness of our Galaxy at the
Solar Neighbourhood as observed from outside the Galaxy. We rely on various
existing optical and infra-red surveys to obtain a multiwavelength estimate. On
the one hand, scattered light does not contribute significantly to the surface
brightness. On the other hand, optical and infrared integrated all-sky surveys
(Pioneer 10/11 and COBE/DIRBE) show a systematically larger value than our
synthetic local estimate based on Hipparcos data. This local estimate is also
compatible with our Galactic simulations normalised at the Solar Neighbourhood
and assuming an homogeneous stellar distribution. We interpret this
disagreement as a signature of the presence of a local minimum of the stellar
density compatible with Gould's belt. According to this result, the global
luminosity of the Milky Way should follow the Tully-Fisher relation established
for external galaxies.
