First of all, before I get on to the windows, Knaresborough is an historic spa town in North Yorkshire not far from Harrogate, York and Leeds. It has the remains of a castle, an impressive stone viaduct over the River Nidd and also features Mother Shipton's caves which I will tell you about on another occasion.
The town has many blank windows in old buildings, especially Georgian ones which were blocked up to avoid window tax or put there to maintain the symmetry of the building. The Town Windows art project replaces the blank windows with a painted panel using a trompe l'oeil effect. They are there all year round and encourage everyone to look around Knaresborough and enjoy different aspects of the town. These are my photos from 2011.
It's all a bit of fun. There is a trail and more information here.