Kengo Kuma and Associates renovated a Siheyuan-style building located exactly in front of the East Gate of the Forbidden Palace (at the heart of Beijing), using hollow blocks of polyethylene. Four types of blocks were produced by rotational molding to be joined and stuck up, as the structure of the extended part. The main structure for the city of Beijing is masonry bricks. Blocks made of polyethylene are in this sense a modern version of masonry. It proves high performance in insulation and passes through light to create a gentle space of Zen, just as the paper did used for Siheyuan in the past.