  Giant radio galaxies are thought to be massive ellipticals powered by
accretion of interstellar matter onto a supermassive black hole. Interactions
with gas rich galaxies may provide the interstellar matter to feed the active
galactic nucleus (AGN). To power radio lobes that extend up to distances of
hundreds of kiloparsecs, gas has to be funneled from kiloparsec size scales
down to the AGN at rates of ~1 Mo yr^-1 during >10^8 years. Therefore, large
and massive quasi-stable structures of gas and dust should exist in the deep
interior of the giant elliptical hosts of double lobe radio galaxies. Recent
mid-infrared observations with ISO revealed for the first time a bisymmetric
spiral structure with the dimensions of a small galaxy at the centre of
Centaurus A (Mirabel et al. 1999, A&A 341, 667). The spiral was formed out of
the tidal debris of accreted gas-rich object(s) and has a dust morphology that
is remarkably similar to that found in barred spiral galaxies. The observations
of the closest AGN to Earth suggest that the dusty hosts of giant radio
galaxies like CenA, are "symbiotic" galaxies composed of a barred spiral inside
an elliptical, where the bar serves to funnel gas toward the AGN.
