The claim is too sweeping to be accurate. Official Brussels tourism and city sources describe Brussels as having an "incredibly diverse street scene," with nearly a thousand Art Nouveau buildings, Art Deco, Brutalism, medieval ruins, and contemporary architecture. The City of Brussels also highlights façades using white stone, yellow bricks, white glazed bricks, and sgraffito, which directly contradicts the idea that Brussels buildings are generally grey. Sources: Visit Brussels, "Architecture in Brussels"; Brussels-Capital Region, "Architecture and heritage"; City of Brussels, "Art Nouveau, Public Art".