Inchindown oil tanks
The Inchindown oil tanks are a group of six underground fuel tanks near Invergordon, Scotland. They are famous for having the longest reverberation time ever recorded in a man-made structure.
Officially they’re called Inchindown, Royal Navy Fuel Tanks, and are also known as the Invergordon Oil Fuel Depot. The five large tanks measure 237 meters (778 feet) long, 9 meters (30 feet) wide, with arched roofs about 13.5 meters (44 feet) high. A sixth tank has the same height and width but is shorter.
Construction started in 1938 and finished in 1941. The tanks were built to provide a bomb-proof supply of furnace fuel oil for the Royal Navy base at Invergordon.
In 2014 the tanks were given Category A listed status, recognizing their national importance. Guided tours were offered in 2009 by Forestry Commission Scotland. After these tours were featured on BBC’s The One Show, acoustics expert Trevor Cox tested the reverberation inside the tanks.
In 2014 Allan Kilpatrick of the Royal Commission on the Ancient and Historical Monuments of Scotland fired a blank pistol inside one tank. Cox recorded the sound and reported very long echoes: about 112 seconds at 125 Hz, 30 seconds at mid frequencies, and 75 seconds across all frequencies.
This page was last edited on 3 February 2026, at 14:40 (CET).