This door by the architectural firm Matharaoo Associates is designed to resemble a sine wave. Now in the home of a diamond merchant in Surat, India, the door measures 5.2m high and 1.7m wide and is made from 40 blocks of teak. Thanks to 160 pulleys and 80 ball bearings, it pushes open easily, despite its weight. More pictures at the link.

Link via Fast Company | Photo: Dinesh Mehta