Londinium, also known as Roman London, was the capital of Roman Britain during most of the period of Roman rule. Most twenty-first century historians think that it was originally a settlement established shortly after the Claudian invasion of Britain, on the current site of the City of London, around 47–50 AD, but some defend an older view that the city originated in a defensive enclosure constructed during the Claudian invasion in 43 AD. Its earliest securely-dated structure is a timber drain of 47 AD. It sat at a key ford at the River Thames which turned the city into a road nexus and major port (which was built between 49 and 52 AD), serving as a major commercial centre in Roman Britain until its abandonment during the 5th century.
Following the foundation of the town in the mid-1st century, early Londinium occupied the relatively small area of 1.4 km (0.5 sq mi), roughly half the area of the modern City of London and equivalent to the size of present-day Hyde Park. In 60 or 61 AD, the rebellion of the Iceni under their queen, Boudica, compelled the Roman forces to abandon the settlement, which was then razed. Following the defeat of Boudica by the Roman governor Gaius Suetonius Paulinus a military installation was established, and the city was rebuilt. It had probably largely recovered within about a decade. During the later decades of the 1st century, Londinium expanded rapidly, becoming Britannia's largest city, and it was provided with large public buildings such as a forum and amphitheatre. By the 2nd century, Londinium had grown to perhaps 30,000 or 60,000 people, almost certainly replacing Camulodunum (Colchester) as the provincial capital, and by the mid-2nd century Londinium was at its height. Its forum basilica was one of the largest structures north of the Alps when Emperor Hadrian visited Londinium in 122. Excavations have discovered evidence of a major fire that destroyed much of the city shortly thereafter, but the city was again rebuilt. By the second half of the 2nd century, Londinium appears to have shrunk in both size and population.
