The south Wales E.coli inquiry was shown images from inside the JE Tudor abattoir in Treorchy, Rhondda.
The inquiry heard that the slaughterhouse had the worst hygiene record in Britain when inspected in 1994.
Conditions at the plant, run by a cousin of the butcher convicted over the E.coli outbreak, were "deteriorating rapidly".
The inquiry was told the abattoir's owners continued to operate, saying they planned to move premises.
The abattoir eventually closed down after the E.coli outbreak when repairs became too uneconomical.