  We aim to study the structure of the nebula around the post-AGB, binary star
89 Her. The presence of a rotating disk around this star had been proposed but
not been yet confirmed by observations. We present high-resolution PdBI maps of
CO J=2-1 and 1-0. Properties of the nebula are directly derived from the data
and model fitting. We also present N-band interferometric data on the extent of
the hot dust emission, obtained with the VLTI. Two nebular components are
found: (a) an extended hour-glass-like structure, with expansion velocities of
about 7 km/s and a total mass ~ 3 10$^{-3}$ Mo, and (b) an unresolved very
compact component, smaller than ~ 0.4" and with a low total velocity dispersion
of ~ 5 km/s. We cannot determine the velocity field in the compact component,
but we argue that it can hardly be in expansion, since his would require too
recent and too sudden an ejection of mass. On the other hand, assuming that
this component is a keplerian disk, we derive disk properties that are
compatible with expectations for such a structure; in particular, the size of
the rotating gas disk should be very similar to the extent of the hot dust
component from our VLTI data. Assuming that the equator of the extended nebula
coincides with the binary orbital plane, we provide new results on the
companion star mass and orbit.
