restrained with far less ornamentation than was common before the 1930s. The most notable architectural feat of this period is the Harbour Bridge. Its steel arch was designed by John Bradfield and completed in 1932. A total of 39,000 tonnes of structural steel span the between Milsons Point and Dawes Point. Modern and International architecture came to Sydney from the 1940s. Since its completion in 1973 the city's Opera House has become a World Heritage Site and one of the world's most renowned pieces of Modern design. It was conceived by Jørn Utzon with contributions from Peter Hall, Lionel Todd, and David Littlemore. Utzon was awarded the Pritzker Prize in 2003 for his work on the Opera House. Sydney is home to Australia's first building by renowned Canadian-American architect Frank Gehry, the Dr Chau Chak Wing Building (2015), based on the design of a tree house. An entrance from The Goods Line–a pedestrian pathway and former railway line–is located on the eastern border of the site. Contemporary buildings in the CBD include Citigroup Centre, Aurora Place, Chifley Tower, the Reserve Bank building, Deutsche Bank Place, MLC Centre, and Capita Centre. The tallest structure is Sydney Tower, designed by Donald Crone and completed in 1981. Regulations limited new buildings to a height of due to the proximity of Sydney Airport, although strict restrictions employed in the early 2000s have slowly been relaxed in the past ten years, with a maximum height restriction now sitting at 330 metres (1083 feet). Green bans and heritage overlays have been in place since at least 1977 to protect Sydney's heritage after controversial demolitions in the 1970s led to an outcry from Sydneysiders to preserve the old and keep history intact, sufficiently balancing old and new architecture. Housing Sydney surpasses both New York City and Paris real estate prices, having some of the most expensive in the world. The city remains Australia's most expensive housing market, with the mean house price at $1,142,212 as of December 2019 (over 25% higher the national mean house price). There were 1.76 million dwellings in Sydney in 2016 including 925,000 (57%) detached houses, 227,000 (14%) semi-detached terrace houses and 456,000 (28%) units and apartments. Whilst terrace houses are common in the inner city areas, it is detached houses that dominate the landscape in the outer suburbs. Due to environmental and economic pressures, there has been a noted trend towards denser