Allerdale Borough Council appointed the practice just before Christmas, ahead of Adjaye Associates, Nissen Adams and artist NK Projects.
McDowell + Benedetti's designs for a £220,000 centrepiece 'cloud' will be used in a shopping street in Workington, Cumbria.
The piece, named 'The Hub', will be accompanied by voice-over work from Martyn Ware, formerly of Eighties band Human League.
The inflated 'cloud' canopy will be suspended by steel cables in the centre of the town, above seating also designed by the young practice.
The seating will feature a 'unique three-dimensional soundscape' composed by specially commissioned musicians, generated from speakers set into the cloud and seating.