How Florida and Colorado are trying to build smart cities from the ground up

Ambitious new cities Songdo and Masdar may not have lived up to their promise, but smaller projects in the US aim to be laboratories for sustainable city planning

Masdar, on the edges of Abu Dhabi, was billed as the world's first sustainable city when it was conceived in 2006. It was intended to be a zero-carbon, zero-waste city, with smart technology embedded across all the city's functions. A decade on and ambitions have cooled. The completion date has moved from 2016 to 2030 and city authorities have said it won't achieve the original aim of being a net zero-emissions city.

Related: Masdar's zero-carbon dream could become world's first green ghost town