London's architectural heritage consists of buildings from a very wide variety of styles and historical periods, with no one of these being dominant. London's distinctive architectural eclecticism stems from its long history, continual redevelopment, destruction by the Great Fire of London and the Blitz, and state recognition of private property rights which have limited large-scale state planning. This sets London apart from other European capitals such as Paris and Rome which are more architecturally homogeneous as a result of being largely rebuilt in neoclassical styles during the 16th-19th centuries. London's diverse architecture ranges from the Romanesque central keep of the Tower of London, the great Gothic church of Westminster Abbey, the Palladian royal residence Queen's House, Christopher Wren's Baroque masterpiece St Paul's Cathedral, the High Victorian Gothic of the Palace of Westminster, the industrial Art Deco of Battersea Power Station, the post-war Modernism of the Barbican Estate and the Postmodern skyscraper 30 St Mary Axe, also known as "the Gherkin".
After the Roman withdrawal from Britain in the 5th century AD, the layout of the Roman settlement governed the plan of the Saxon and medieval city. This core of London is known as the City of London, while Westminster, the ancient centre of political power, lies to the west. Relatively few medieval structures survive due to the city's near-total destruction in the Great Fire of London in 1666, with exceptions such as the Tower of London, Westminster Abbey, Westminster Hall, Guildhall, St James's Palace, Lambeth Palace and some Tudor buildings. After the Great Fire, London was rebuilt and greatly modernised under the direction of the baroque architect Sir Christopher Wren, with the new St Paul's Cathedral as its centrepiece.
After a period of dramatic expansion in the 18th and 19th centuries, London reached its zenith as the world's largest and populous city from 1831 to 1925, becoming the capital of the British Empire at its greatest extent and power. In this period London sprawled vastly beyond its historical boundaries, absorbing many formerly rural settlements and creating vast suburbs. The city was further transformed by the Industrial Revolution as infrastructure projects like the West India Docks, the Regent's Canal, intercity railway termini like Paddington Station and the world's first underground railway system set London apart as the pre-eminent city of the industrial age. London endured significant destruction during The Blitz of World War II, leading to approximately 1.5 million people being made homeless. This led to the construction of many modernist housing estates in The Post-War period. Some of these were built in a distinctive brutalist style such as at The Barbican Estate and Trellick Tower. London also declined economically in this period, with many former industrial areas fall into dereliction. However, in the 1980s onwards, largely as a result of a re-surgent economy based around financial services, areas like the Isle of Dogs were re-vitalised with the development of substantial new office buildings such as One Canada Square (1991) one of London's first true skyscrapers.Throughout most of London's history, the height of buildings has been restricted. These restrictions gradually eroded in the post-war period (except those protecting certain views of St Paul's Cathedral). High-rise buildings have become more numerous since, particularly in the 21st century. Skyscrapers are now numerous in the City of London financial district and Canary Wharf: a new financial district created in the 1980s and 1990s in the former London docklands area of the Isle of Dogs. Examples of such buildings include the 1980s skyscraper Tower 42, the radical Lloyd's building by Richard Rogers, One Canada Square: the centre piece of the Canary Wharf district and 30 St Mary Axe (nicknamed "the Gherkin") which set a precedent for other recent high-rise developments to be built in a similar high-tech style. Renzo Piano's The Shard completed in 2012 set a significant milestone by becoming London's first 'supertall' skyscraper due to its exceeding 1000 ft (304.8m) in height.
Prehistoric
Although no pre-Roman settlement is known, there were prehistoric crossing points at Deptford and Vauxhall Bridge, and some prehistoric remains are known from archaeology of the River Thames. It is likely that the course of Watling Street follows a more ancient pathway. Ancient Welsh legend claims the city of the Trinovantes – dedicated to the god Lud (Caer Llud) – was founded by the followers of Brân the Blessed, whose severed head is said to be buried under the White Tower facing the continent.
Roman London (60–500 CE)
Londinium was initially founded as a military trading port, while the first capital of the province was at Camulodunum. But after the Boudican Revolt of 61, when both cities were razed to the ground, the capital was removed to London, which rapidly grew to pre-eminence with the establishment of a Forum and a provincial Praetorium. The city was originally laid out to a classical plan like many other cities in Britannia and throughout Europe, in a roughly rectangular form with the south side formed by the River Thames, and divided into blocks of insulae.London Archaeology; Vol 15 Spring 2018 Two east–west streets (now Cheapside and Lower Thames Street) led from Newgate and Ludgate to form the cardo, presumably leading to a lost gate (or gates) at the present location of the Tower of London with the road to Canterbury and Dover. An extension of Watling Street formed the decumanus maximus, crossing the river from Billingsgate over the ancient London Bridge to Southwark and the south coast road beyond. The Forum was located at the current site of Leadenhall Market, and is said to have been the largest building north of the Alps in ancient times; remains can still be visited in the basement of some of the market shops.
The rectangular walled and gridded city was soon extended to the west over the River Walbrook, north towards marshy Moorfields and east to the area later known as Minories.London Archaeology, Ibid A Romano-British tomb sculpture of an eagle was found there in 2013, suggesting that the Minories lay outside the city boundary in the early second century. Part of the amphitheatre remains beneath the London Guildhall square; a Roman bathing complex is accessible in the basement of 100 Lower Thames Street. The square Castrum was located at the north-east of the city at the Barbican, close to the Museum of London where part of the Roman London Wall remains. For centuries afterward, distances from London were reckoned from the London Stone, once claimed to be a fragment of masonry from the ancient Thames-side Praetorium. Late Roman private houses of leading Christians are thought to have been the foundation of the earliest churches; mosaic remains in the crypt at All Hallows by the Tower and perhaps some at St Paul's Cathedral.
The Middle Ages: Romanesque, Gothic and Tudor (1066–1603)
After the Roman abandonment of Britain in the 5th-century, the approximate format of the Roman city of Londinium continued to form the structural basis of London’s medieval core now known as The City of London, from which the entire modern-day city initially expanded. Little remains of London's medieval architecture due to the city's near-complete destruction in the Great Fire of London of 1666, but a handful of scattered survivors as well as other records provide a vivid picture of the London’s architectural character in this period. From the beginning of The Middle Ages until the late 16th century, London lay predominantly within the boundaries of its city walls that were originally built by The Romans – the area now known as the City of London – with Westminster being a separate smaller settlement to the west. These city walls were continually repaired and enhanced throughout the Middle Ages, functioning as the city’s primary means of defence. These walls contained seven main fortified gates: Aldersgate, Aldgate, Bishopsgate, Cripplegate, Ludgate, Moorgate and Newgate, the last of which also functioning as an infamous prison. But during the 18th century most of the city walls were demolished to facilitate the dramatic expansion of the city in an era in which they were no longer necessary. Small fragments of these walls still survive in places such as The Barbican and London Wall.By the late 16th-century there was substantial development outside of London's city walls, such as along The Strand, in Lincoln's Inn Fields, in Smithfield – and on the south bank of the Thames at Southwark, with London Bridge connecting the latter to the rest of the city to the north. Being the only bridge across the Thames within the city, London Bridge was an exceptionally significant structure that connected London to the economically, politically and religiously significant areas in the South-East of England such as Canterbury, the most important site of pilgrimage in late medieval England. The earliest record of London bridge dates from the 10th century, a structure probably built of wood, but the best-known incarnation was constructed between 1176 and 1209. This was a stone bridge 900 ft wide with 19 arches, complete with its own street of shops, houses, a chapel and a drawbridge in the centre to allow large boat traffic to pass through. The buildings on the bridge were eventually demolished in 1761 and this medieval incarnation of the bridge which survived for over six centuries was finally replaced by a far more uniform classical style design in 1831. With only one bridge for the entire middle-ages, the river Thames was the main means of transportation within the city, as well as providing access to overseas trade by sea; many wharves and quays lined its north bank. Romanesque and Gothic Many of medieval London's most significant structures were initially constructed by the Normans in the late 11th and 12th-century. Although it is a common mis-conception that the Norman's brought the Romanesque style of architecture to England — the Anglo-Saxons had already built several substantial churches in the style, most notably the first Westminster Abbey in 1052 — Romanesque buildings built in England after 1066 were far more ambitious in terms of size and style, as well as far more numerous in terms of the number of buildings commissioned. Almost immediately after their conquest of England the Normans built several fortresses along the River Thames in the center of London to consolidate their power within the city, most notably the Tower of London which survives today. The White Tower, the central keep of the complex, was completed in the 1080s in a Romanesque style and was the tallest building in the city. It served multiple functions: a fortress, prison, the seats of government and a royal residence for William the Conqueror. One of the oldest and least altered Romanesque churches in England is also built inside the White Tower: the chapel of St John's. The only other surviving Romanesque church in central London is St Bartholomew-the-Great in Smithfield, the remains of a much larger priory church founded in 1123. The Tower of London complex reached its approximate current format with two outer defensive walls by the end of the 13th century.