Londinium was a settlement established on the current site of the City of London. Early Londinium occupied a relatively small area of 1.4 km2 (0.5 sq mi), roughly equivalent to the size of present-day Hyde Park, with a fortified garrison on one of its hills.
The map below shows Londonium according to Britanica.com
During the later decades of the 1st century, Londinium expanded rapidly, becoming Great Britain’s largest city. By the turn of the century, Londinium had grown to perhaps 30 thousand or 60 thousand people, almost certainly replacing Camulodunum as the provincial capital.