Danish architecture studio BIG and Dutch studio Barcode Architects have unveiled the angular Sluishuis housing block above the IJ lake in Amsterdam's IJburg district. Built on an artificial island in the IJ lake, the square housing block surrounds an internal harbour with a double cantilever that forms a gateway from the lake.Described by the architecture studios as a new landmark for IJburg, the housing development contains 442 owner-occupied and rental apartments. The building has a distinctive shape, with blocks on two sides of the square cantilevered to create a cut-out above the water and the other two blocks stepping down to create terraces with apartments opening out on top balconies.The four blocks enclose a courtyard that steps down to the water. On the ground floor, opening up to the courtyard, are a sailing school, a water sports centre and a restaurant with a large terrace.Above the ground floor the blocks, which were clad in aluminium to reflect the surrounding water, contain a range of different-sized apartments from studios to penthouses. The top two floors contain duplex penthouses, while the apartments within the cantilever have views directly down to the water.Where the blocks step down to create terraces they are clad in timber to contrast with the external aluminium finish.Two long staircases climb the two angled facades leading to a public green roof and garden with a rooftop walkway.