IN a coincidence as strange and rare as it would be if a comet was to appear in the sky when Forest wins a match, two art exhibitions held in former prison cells are taking place in Nottingham this month.

One, put on by Nottingham Contemporary, is titled The Impossible Prison and is held in the Galleries of Justice from October 31. But the other is the annual Open festival of contemporary visual art, an event not to be confused with the Open at the Castle and which is a kind of celebration of the city's many artist groups and studios.

This year its main event takes place in the "Art Salon", the newly refurbished adjunct to The Art Organisation (TAO) gallery in Station Street which used to be a police station including cells and interview rooms. The structure of the place means there are lots of little rooms in which to wander, the smallest of the rooms remaining the cells, which still come with graffiti and spy holes. Now painted a lurid dark red, the cells have a creepy, claustrophobic air which doesn't encourage you to linger too long. In fact, they have a slight sense of Hell about them.

Hell or not, the venue has attracted artists from 14 studio and artist groups and as such the contributor list reads like an A-Z directory of Nottingham visual artists. Many also have work on view elsewhere. Painter Simon Withers, for example, currently has a show at the other Open at the Castle; Jackie Berridge, of Harrington Mill Studios in Long Eaton, who paints naïf children's scenes, was showing at the Southwell Open Studios last weekend; so was Stuart Blackwood, who also has photographs in the Castle Open; the painting of embracing Jewish and Arab children, by an artist known as PopX, was previously shown at TAO; and so on.

Stand-outs in this entertaining show, dominated by painting, may include Pauline Lucas' crafted charcoal/graphite drawing – showing near the entrance to Interview Room No. 1. Next door hang several savage satires by Mark D, Nottingham's own Stuckist who's sticking a rigid digit up at celebrity culture. But most wicked of all are the mock books created by D.A. Orli, of Sneinton Artists.

Orli's framed collection of seemingly innocuous I-Spy titles fool you for a half-minute until your eye and brain take in the full gamut of their titles: I-Spy Council Incompetence, I-Spy Illegal Immigrants, I-Spy Police Brutality, I-Spy The Dead …lovely. Next to them hangs a framed collection of what appear to be musty, dusty, Edwardian children's instructional books with decorative covers. Titles here include the charming Kitty Enamelling and Collecting and Mounting Elf and Fairy Species. The pictorial designs are perfect, the sense of humour evil. Let's see more of Orli!

"We've got all the artist groups here apart from The Stand Assembly, who have been moving venue," says Rob Howie Smith, TAO leader and photographer, whose black and white images can also been seen at the exhibition. "They all reacted very well to the gallery. What I didn't want was for this venue to be yet another white wall gallery space, and it isn't."

The Open can be seen until November 1.