Inchindown oil tanks

[1] The tanks hold the record for the longest reverberation in any man-made structure, surpassing the Hamilton Mausoleum in 2014.

They were built to be a bomb-proof supply of furnace fuel oil to the Royal Navy's base at Invergordon.

[5] In 2009, guided tours of the tanks were offered by Forestry Commission Scotland.

[6] After the tours were mentioned on BBC television programme The One Show, professor of acoustic engineering at the University of Salford Trevor Cox was motivated to perform reverberation tests in the underground tanks.

[2] In 2014 Allan Kilpatrick from the Royal Commission on the Ancient and Historical Monuments of Scotland fired a pistol blank inside one of the tanks.