London

===Topography===
[[File:London from Primrose Hill May 2013.jpg|thumb|London from [[Primrose Hill]]]]
Greater London encompasses a total area of {{convert|1583|km2|sqmi|order=flip}} an area which had a population of 7,172,036 in 2001 and a population density of {{convert|4542|PD/km2|PD/sqmi|order=flip}}. The extended area known as the London Metropolitan Region or the London Metropolitan Agglomeration, comprises a total area of {{convert|8382|km2|sqmi|order=flip}} has a population of 13,709,000 and a population density of {{convert|1510|PD/km2|PD/sqmi|order=flip}}.<ref name=Metrop>{{Cite web |url=http://www.dgcl.interieur.gouv.fr/sections/a_votre_service/lu_pour_vous/les_grandes_metropol/downloadFile/attachedFile/metropolislondres.pdf?nocache=1254397828.63 |title=Metropolis: 027 London, World Association of the Major Metropolises |access-date=3 May 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110427084411/http://www.dgcl.interieur.gouv.fr/sections/a_votre_service/lu_pour_vous/les_grandes_metropol/downloadFile/attachedFile/metropolislondres.pdf?nocache=1254397828.63 |archive-date=27 April 2011}}</ref>

Modern London stands on the [[River Thames|Thames]], its primary geographical feature, a [[Navigability|navigable]] river which crosses the city from the south-west to the east. The [[Thames Valley]] is a [[floodplain|flood plain]] surrounded by gently rolling hills including [[Parliament Hill, London|Parliament Hill]], [[Addington Hills]], and [[Primrose Hill]]. Historically London grew up at the [[lowest bridging point]] on the Thames. The Thames was once a much broader, shallower river with extensive [[marsh]]lands; at high tide, its shores reached five times their present width.<ref name=london_065>{{Cite book |url=https://books.google.com/books?id=M9qvtYYhRtAC&pg=PR11 |title=London: A History |first=Francis |last=Sheppard |page=10 |publisher=Oxford University Press |year=2000 |isbn=978-0-19-285369-1 |access-date=6 June 2008}}</ref>

Since the [[Victorian era]] the Thames has been extensively [[Thames Embankment|embanked]], and many of its London [[Tributaries of the River Thames|tributaries]] now flow [[Subterranean rivers of London|underground]]. The Thames is a tidal river, and London is vulnerable to flooding.<ref name=london_066>{{Cite web |url=http://www.environment-agency.gov.uk/yourenv/eff/1190084/natural_forces/flooding/?version=1&lang=_e |title=Flooding |publisher=UK [[Environment Agency]] |access-date=19 June 2006 |archive-url=https://web.archive.org/web/20060215080725/http://www.environment-agency.gov.uk/yourenv/eff/1190084/natural_forces/flooding/?version=1&lang=_e |archive-date=15 February 2006 |url-status=dead}}</ref> The threat has increased over time because of a slow but continuous rise in [[Tide|high water]] level caused by [[climate change]] and by the slow 'tilting' of the British Isles as a result of [[post-glacial rebound]].<ref name=london_067>{{Cite web |url=http://www.environment-agency.gov.uk/yourenv/eff/1190084/natural_forces/sealevels/?version=1&lang=_e |title="Sea Levels"&nbsp;– UK Environment Agency |publisher=[[Environment Agency]] |access-date=6 June 2008 |archive-url=https://web.archive.org/web/20080523225152/http://www.environment-agency.gov.uk/yourenv/eff/1190084/natural_forces/sealevels/?version=1&lang=_e |archive-date=23 May 2008 |url-status=dead}}</ref>