As war loomed in 1938, work began to prepare industrial Leeds for the expected aerial attacks.
The city's armaments factories - including the Barnbow and Kirkstall Forge - made it a target for Nazi air raids, and the building of large public shelters was sanctioned.
Most of them were sited under parks and recreation grounds and still exist today - albeit with their entrances sealed off.
However, some evidence of their presence, such as raised mounds and ventilation shafts, can still be seen.
One of the most heavily fortified can be found in a quarry in Adel Woods, on the northern edge of the city. It was actually never intended to shelter people - instead it was built as a secure storage unit for valuable documents, well away from the city centre.
The bunker was commissioned by the Leeds Permanent Building Society, who installed an armoured steel door and reinforced concrete. The waterproof structure had two levels and an electricity supply. An access road was built for vehicles transporting documents. Leeds Corporation were also given permission to use the bunker to protect some of the city's treasures, including the 17th-century founding charter granted by King Charles II.
Halifax Bank, which took over the building society in 1995, later revealed that the deeds stored during the war years were worth over £100million. They were removed from their previous home at the Permanent House offices and taken to the bunker, which had 25,000 cubic feet of space. They were retrieved in 1945 and the shelter dismantled and sealed a year later.
The bricked-up entrance, located in a steep bank off Stairfoot Lane, can still be seen today.
There is a shelter under Woodhouse Moor with a raised mound still visible, and some concrete patches in the grass which indicate the sites of the escape hatches.
There was a small shelter at the bottom end of Soldiers Field in Roundhay, off Princes Avenue, and a larger one beneath Potternewton Park.
Other shelters were constructed at Cross Flatts Park in Beeston, East End Park, Chapel Allerton Park, Wortley, Armley, York Road, and the Buslingthorpe recreation ground in Chapeltown, now called Norma Hutchinson Park, where raised manhole covers can be seen.
Trenches would be dug and a concrete floor laid before bench seating was installed. Some shelters were segregated, with separate areas for men and families. Some had a water supply, and most had wardens and toilets.
Leeds suffered nine air raids during the war years, fewer than first feared.