section_path: Geography/Architecture
section_name: Architecture
paragraph_text: Architecture
  
  London's buildings are too diverse to be characterised by any particular architectural style, partly because of their varying ages. Many grand houses and public buildings, such as the National Gallery, are constructed from Portland stone. Some areas of the city, particularly those just west of the centre, are characterised by white stucco or whitewashed buildings. Few structures in central London pre-date the Great Fire of 1666, these being a few trace Roman remains, the Tower of London and a few scattered Tudor survivors in the city. Further out is, for example, the Tudor-period Hampton Court Palace.
  
  Part of the varied architectural heritage are the 17th-century churches by Christopher Wren, neoclassical financial institutions such as the Royal Exchange and the Bank of England, to the early 20th century Old Bailey courthouse and the 1960s Barbican Estate. The 1939 Battersea Power Station by the river in the south-west is a local landmark, while some railway termini are excellent examples of Victorian architecture, most notably St. Pancras and Paddington. The density of London varies, with high employment density in the central area and Canary Wharf, high residential densities in inner London, and lower densities in Outer London.
  
  The Monument in the City of London provides views of the surrounding area while commemorating the Great Fire of London, which originated nearby. Marble Arch and Wellington Arch, at the north and south ends of Park Lane, respectively, have royal connections, as do the Albert Memorial and Royal Albert Hall in Kensington. Nelson's Column (built to commemorate Admiral Horatio Nelson) is a nationally recognised monument in Trafalgar Square, one of the focal points of central London. Older buildings are mainly brick, commonly the yellow London stock brick.
  
  In the dense areas, most of the concentration is via medium- and high-rise buildings. London's skyscrapers, such as 30 St Mary Axe (dubbed "The Gherkin"), Tower 42, the Broadgate Tower and One Canada Square, are mostly in the two financial districts, the City of London and Canary Wharf. High-rise development is restricted at certain sites if it would obstruct protected views of St Paul's Cathedral and other historic buildings. This protective policy, known as 'St Paul's Heights', has been in operation by the City of London since 1937. Nevertheless, there are a number of tall skyscrapers in central London, including the 95-storey Shard London Bridge, the tallest building in the United Kingdom and Western Europe.
  
  Other notable modern buildings include The Scalpel, 20 Fenchurch Street (dubbed "The Walkie-Talkie"), the former City Hall in Southwark, the Art Deco BBC Broadcasting House plus the Postmodernist British Library in Somers Town / Kings Cross and No 1 Poultry by James Stirling. The BT Tower stands at 620 feet (189 m) and has a 360 degree coloured LED screen near the top. What was formerly the Millennium Dome, by the Thames to the east of Canary Wharf, is now an entertainment venue called the O Arena.