  We present an HST imaging study of the nearby (4 Mpc distant) Circinus
galaxy, which contains the nearest type 2 Seyfert nucleus and prominent
circumnuclear star formation. Images have been obtained in the
[OIII]$\lambda$5007, H$\alpha$ and H$_2$ v=1--0 S(1) emission lines, and in the
green (5470 \AA), red (8140 \AA) and near infrared (2.04 and 2.15 $\mu$m)
continua. An image in the [Fe II] $\lambda$1.644 $\mu$m line has been taken
with a ground-based telescope. The [OIII] and H$\alpha$ images reveal the
detailed structure of the complex of streamers and knots of high-excitation
gas, which extends out of the galaxy disk. The morphology some 250 pc from the
nucleus strongly suggests that the high-excitation gas is concentrated on the
surface of a hollow cone with apex close to the nucleus. Such a structure may
result through entrainment of dense gas from a circumnuclear torus in the
galaxy disk by a low density, outflowing wind or jet. Within 40 pc of the
nucleus, the high-excitation gas takes the form of a striking, filled V-shaped
structure extending in the same direction as the larger scale high-excitation
emission. This `V' can be described as an ionization cone, though a
matter-bounded structure is also possible. The implied collimation of the
ionizing photons or gaseous outflow must occur within 2 pc of the apex of the
cone, presumed to be the location of the nucleus. The H$\alpha$ image shows a
complex structure of HII regions, including the well known starburst ring of
radius 150 - 270 pc. In addition, there is a more compact (40 pc radius),
elliptical ring of HII regions around the `ionization cone'. We argue that this
latter ring, which we call the nuclear ring, is intrinsically circular and
located in the plane of the galaxy disk. Abstract truncated.
