It was followed by Silicon Valley (2nd), Dublin (3rd), Bangalore (4th), Boston (5th), Shanghai (6th) and New York (7th).
"The £15.8bn Crossrail project is the largest transport scheme in Europe, while new university campuses such as the £1bn campus for Imperial College London in White City, which is being planned as London’s first major research quarter, are establishing new networks between business and education," it said.
Another sweet spot was London Underground's £1bn extension of the Northern line to Battersea and Nine Elms.
JLL's city momentum index measures the dynamism of urban economies, as well as how well they are embracing technological and infrastructure transformation.
"City momentum... is crucially about building the foundations of an innovation-orientated economy through technology, creating cutting-edge new businesses, attracting talent and nurturing vibrant inclusive communities," it said.