St Andrew's House is the H.Q. of the Scottish Government, found East of Princes Street under Calton Hill.
Built on the site of the old Calton Jail, the imposing Orwellian hulk was the largest metal-framed building in Europe on its completion in 1939.
The occupation of the building also marked the first time government departments serving Scotland were brought under the same roof in Edinburgh.
It took decades to complete and opened as war was declared in Europe with the graves of ten murderers from Calton Jail still buried under the car park.