A company is trying to unravel the mystery of a secret World War II bunker beneath a former steelworks.
The bunker is beneath the former Corby steelworks
Steel firm Corus is trying to discover the purpose of the underground complex at its site in Corby, Northants.
The bunker, made from cement, includes a wide range of telephone equipment. It also includes some blocked up tunnels.
Bernard Curran, human resources director for Corus, said the firm would particularly like to hear from anyone who worked at the facility.
"We'd like to hear from anyone who can recall what the facility was built for," he said.