THE POLYGON GALLERY, VANCOUVER, CANADA - FINALIST: Riba describes this gallery, by Patkau Architects, as 'a new cultural hub on the decaying industrial waterfront of North Vancouver, a self-contained township with its own industrial and maritime heritage'. It adds that the gallery, completed in 2017, replaces a 'failing 1970s photography museum' and is raised more than a metre above ground level to allow for rising sea levels. The diagonal panels on the roof, fitted with windows, invite natural light inside. Riba says: 'This is a gallery with no permanent collection so it has to work hard to produce its own identity – something the architecture helps it achieve'