Architecture. Main articles: Architecture of London and List of tallest buildings and structures in London

Main articles: Architecture of London and List of tallest buildings and structures in London

30 St Mary Axe, also known as the Gherkin, towers over St Andrew Undershaft

London's buildings are too diverse to be characterised by any particular architectural style, partly due to 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, England's oldest surviving Tudor palace, built by Cardinal Thomas Wolsey circa 1515. Wren's late 17th century churches and the financial institutions of the 18th and 19th centuries such as the Royal Exchange and the Bank of England, to the early 20th century Old Bailey and the 1960s Barbican Estate form part of the varied architectural heritage.

The disused, but soon to be rejuvenated, 1939 Battersea Power Station by the river in the southwest 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, high residential densities in inner London and lower densities in the suburbs.

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 is a nationally recognised monument in Trafalgar Square, one of the focal points of the city centre.

Buckingham Palace is the official residence of the British monarch

High-rise development is restricted at certain sites if it would obstruct protected views of St Paul's Cathedral. Nevertheless, there are plans for more skyscrapers in central London (see Tall buildings in London), including the 72-storey Shard London Bridge which is currently under construction. Development temporarily stalled as a result of the recent financial crisis, but is reported to be recovering.

Older buildings are mainly brick built, most commonly the yellow London stock brick or a warm orange-red variety, often decorated with carvings and white plaster mouldings.

In the dense areas, most of the concentration is achieved with medium- and high-rise buildings. London's skyscrapers such as 30 St Mary Axe, Tower 42, the Broadgate Tower and One Canada Square are usually found in the two financial districts, the City of London and Canary Wharf. Other notable modern buildings include City Hall in Southwark with its distinctive oval shape, and the British Library in Somers Town/Kings Cross. What was formerly the Millennium Dome, located by the Thames to the east of Canary Wharf, is now used as an entertainment venue called The O2 Arena.