Spaghetti Junction, officially called the Gravelly Hill Interchange, is at junction six on the M6 motorway in BirminghamPhotograph: Andrew FoxThe junction will be 40 years old on 24 MayPhotograph: Andrew FoxThe interchange was given its nickname by a Birmingham newspaper reporter who likened it to a plate of spaghettiPhotograph: Andrew FoxThe junction took 11 years to plan and four years to build, costing £10.8mPhotograph: Andrew FoxThe 30-acre site is supported by 559 concrete columns up to 80 feet highPhotograph: Andrew FoxIt spans several roads, two rivers, two railway lines and three canalsPhotograph: Andrew FoxThe site was supposedly of such strategic importance that it was thought to be a nuclear bomb target for Russia in the Cold WarPhotograph: Andrew FoxIn 2009, the interchange was voted Britain's most intimidating road systemPhotograph: Andrew FoxIt was originally designed to take 75,000 vehicles a day, but it now deals with twice that amount. In its 40-year history there has been close to 2bn vehicles passing throughPhotograph: Andrew Fox