The Art Gallery of Ontario (AGO) has 45,000 square metres (480,000 sq ft) of physical space, making it the eighth largest art museum in North America. Its collection includes more than 80,000 works spanning the 1st century to the present day. As a multiuse facility and complex programming venue, AGO caters to a very broad audience through a mandate of maintaining the permanent collection for the people of Ontario and as an educational institution.

Layered lighting applications increase current museum light levels while revealing important ar­chitectural features. Throughout public spaces, there is recessed star-patterned down and accent lighting, with linear indirect washlighting at prominent architectural elements. In the galleries, Power Bar track lighting, which is completely removable, allows for ultimate flexibility for rotating exhibits. Uplights graze the façade’s curving structural elements, and exterior flood lighting highlights facade graphics.

L'Observatoire's scope included the exterior and all interior spaces of the Gehry extension including all galleries, the baroque stair and the Gehry designed shop.