The Canberra Central district is substantially based on Walter Burley Griffin's designs. In 1967 the then National Capital Development Commission adopted the "Y Plan" which laid out future urban development in Canberra around a series of central shopping and commercial area known as the 'town centres' linked by freeways, the layout of which roughly resembled the shape of the letter Y, with Tuggeranong at the base of the Y and Belconnen and Gungahlin located at the ends of the arms of the Y.