It must be the Biennial because the popular Caravan Gallery is here, or rather it was.
It was in the front courtyard outside the Bluecoat (a bit more up-market than previous visits!) for the first few days of the festival before moving onto Portsmouth. I think Liverpool was their driest stop of the whole Summer.
You can find out more and buy some really funny stuff on the website:
www.thecaravangallery.co.uk