A UNIQUE piece of First World War architecture, built in 1917 to protect Sunderland from Zeppelin attacks has re-opened following a £68,000 restoration.

Fulwell Acoustic Mirror’s historic value went unrecognised for many years and its deterioration led to its inclusion on the Historic England - previously known as English Heritage - Heritage at Risk register.

This triggered a partnership between Sunderland City Council, Historic England and Limestone Landscape which has led to its sympathetic restoration.

The Acoustic Mirror was built to help detect German airships following a series of Zeppelin raids on the North-East coastline during 1915 and 1916.

It was designed to act as an acoustic early warning system against air raids, after a bomb dropped by a Zeppelin over the Wheatsheaf area of Sunderland in April 1916 left 22 people dead and more than 100 injured.

The mirror worked by reflecting sound detected by a microphone in front of the dish to an operator who could alert the authorities of approaching Zeppelins.

Using sound detection methods learnt in the trenches it was designed to give a 15-minute warning of approaching enemy airships

Today, the concrete structure, with its rendered concave dish tilted upwards to watch the sky, is one of only six acoustic mirrors built during the First World War to survive. It is also one of only 10 scheduled ancient monuments in Sunderland.

In 2013 Sunderland City Council secured funding from Historic England. This, together with money allocated to Limestone Landscape Partnership from the Heritage Lottery Fund (HLF), allowed work to go ahead to save the structure and enabled it to be taken off the Heritage-At-Risk register.

Councillor John Kelly, the council's portfolio holder for public health, wellness and culture, said: "Fulwell Acoustic Mirror is a very rare, long lost reminder of the home front in the North-East during the First World War.

"The restoration has give the acoustic mirror a new lease of life by preserving it for future generations almost a hundred years after it was build to defend our shores.

"This along with new interpretative material will make it more accessible to residents, groups, schools and visitors as a unique heritage tourist attraction and educational resource."

Sited 300 metres north-west of Fulwell Windmill, access to the site is along a track off the A1018 Newcastle Road, behind the VW garage next to Fulwell Mill.