  The observed gas dynamics in the Milky Way can only be explained by a bar in
the galactic center. Such a bar is directly visible in the near-IR maps of the
bulge, where it causes a distinctive asymmetric light distribution pattern.
Another large-scale structure is the grand-design 4-arm spiral pattern, most
clearly observed in the spatial distribution of molecular gas and HII-regions.
  In order to model the observed gas flow structure, we constructed a model for
the stellar mass distribution. For the inner 5 $\kpc$ we used the 3D
deprojected near-IR light distribution, as observed by the COBE/DIRBE
experiment, and added an analytical disk model outside the box as well as a
halo model. With this frozen mass distribution, we computed the stationary gas
flow for various deprojection parameters and pattern speeds. For all reasonable
parameter choices, we obtain a 4-armed spiral pattern, which can be matched to
the observed spiral arms.
  In the bar region, our model can explain the non-circular motion visible in
the terminal velocity curve as well as part of the forbidden velocities. Inside
the corotation, we also find 4 spiral arms, the nearest arm corresponds to the
3-kpc-arm, although only qualitatively. The missing southern 3-kpc-arm at the
far end of the galaxy is explained by running parallel to another arm. Close to
the center, we find gas on circular orbits forming a disk. Such a disk has been
observed in emission of the CS molecule, however only part of the disk appears
to be occupied by dense enough gas to be traced by CS. Further we compare our
model to the distribution of OH/IR stars in the inner galaxy.
