  Near-infrared images of the prototype LINER / Seyfert 1 galaxy NGC 1097
observed with the Very Large Telescope (VLT) using adaptive optics disclose
with unprecedented detail a complex central network of filamentary structure
spiralling down to the center of the galaxy. The structure, consisting of
several spiral arms, some almost completing a revolution about the center, is
most prominent within the radius of about 300 pc. Some filaments can be traced
further out, where they seem to connect with the nuclear star-forming ring at
0.7 kpc radius. Straight principal shocks running along the primary large-scale
bar of NGC 1097, seen in the optical images as prominent dust lanes, curve into
this ring, but radio polarization vectors cross the nuclear ring under a rather
large angle. Here we attempt to explain this morphology in terms of
three-dimensional gas flow in a barred galaxy. In our scenario, parts of the
principal shock, which propagate in the off-plane gas, can cross the nuclear
star-forming ring, and excite waves inward from it. If the dispersion relation
of the excited waves allows for their propagation, they will naturally take the
shape of the observed central spiral. The nuclear region of NGC 1097 remains
unresolved at sub-arcsec scales in the near-IR, with an upper size limit of <10
pc FWHM. Thus, any putative central dusty torus or gaseosus disk envisaged by
the AGN unified schemes has to be smaller than 10 pc in diameter at near-IR
wavelengths. The extinction in the region between the nuclear star-forming ring
and the nucleus increases very moderately, reaching A_v~1 at the immediate
surrounding of the nucleus. Thus, if the nuclear filaments are tracing cold
dust, they contribute to a very low extinction in the line of sight and are
likely to be distributed in a rather thin disk.
