Architecture studio OMA has completed its extension to the Musée National des Beaux-Arts du Quebec, which features a stack of stepped galleries and a protruding, angular staircase.
The Pierre Lassonde Pavilion ? named after the chair of the museum's board of directors ? is due to open tomorrow in Quebec's Parc des Champs-de-Bataille.

OMA's New York office worked with local firm Provencher Roy on the 14,900-square-metre building, which is its first project in Canada and described as the largest cultural project in Quebec City.
The new structure is designed as a gateway between the park and the busy Grande Allée thoroughfare, and a link to the museum's three existing buildings from the main road.
"The building aims to weave together the city, the park and the museum as an extension of all three simultaneously," said the OMA team, which is led by partner Shohei Shigematsu.
Galleries are housed in three main volumes that step down in section towards the park, becoming wider in plan each time. The building increases the museum's exhibition space by 90 per cent.
As part of the stacked arrangement, the top volume cantilevers 20 metres out towards the street. This creates a 12.6-metre-high Grand Hall underneath, which serves as a urban plaza for the museum's public functions and provides access to the galleries, courtyard and auditorium.
The projecting structure is supported by a steel truss system, which allows for a column-free layout inside.

While the Grand Hall...