High in the treetops overlooking a bend of the city river, there is a secret city hiding in plain sight.

This city can be found near the Cathedral and beside the ruins of Cow Tower, a remnant of Norwich's once mighty medieval defences.

It may appear to some as a large collection of birdhouses but it is actually an architectural installation designed to symbolise the connection between nature and our urban surroundings.

Norwich Evening News: Spontaneous City appeared in 2011 as part of a city festivalSpontaneous City appeared in 2011 as part of a city festival (Image: Creative Commons/Michael Dibb)

The Spontaneous City was built as part of the Norwich and Norfolk Festival in 2011 and is made up of more than 400 wooden boxes of different sizes. 

Its design, which expands as the tree grows, allows it to support the local bird population, insects and other creatures. 

The miniature city was created by London-based Jo Joelson and Bruce Gilchrist and installed by local tree surgeons.

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Ms Joelson said at the time: "It is an art project but also viable bird and bug houses.

"First, we identified which trees we wanted to use, carried out surveys on them and designed these suitable structures.

"It aims to encourage people to interact with the tree and spend time looking at it and using it as inspiration.

Norwich Evening News: The installation is located next to Cow Tower at the edge of the River WensumThe installation is located next to Cow Tower at the edge of the River Wensum (Image: Newsquest)

Mr Gilchrist added that there are many layers to the work they created.

He said: "There has been a huge decline in bird populations. These are effectively empty houses.

"Where have they all gone? Spontaneous City is a symbol of crisis in nature."