Run for the hills, they’ve landed! Oh no wait, it’s not the mothership from a B-movie incoming extra-terrestrial invasion, but the new extension to the Stedelijk Museum in Amsterdam. It is certainly alien, however. Berthed incongruously next to its parent building in the same square as such classical buildings as the Rijksmuseum and the Van Gogh Museum, the Stedelijk extension is as much from another world as it can be; big, and scary, albeit white instead of green. Viewed from the back it resembles a giant manta ray, and from underneath my bathroom sink.

Inside though, things start to look up considerably. Dutch firm Benthem Crouwel Architects have echoed some of the cherished themes of the neighbouring 1890s building, such as the staircase – which provides a central spine. The designers hope that visitors, while appreciating the new building’s unique style, will feel it an “integrated addition”, flowing seamlessly from the old into the new. That may be so, and we really like what they’ve done with the inside, but I’m not sure if the pedestrians outside will be so swept along.

Photography, John Lewis Marshall