In its ultimate grandiose form, Londinium’s basilica, the city’s first civic centre, was the largest building of its day, and in fact was the largest building of its type west of the Alps.
Located where Gracechurch Street now stands, the first basilica, which served as a town hall and law courts, was first erected in 70AD on high ground to the east of the now hidden Walbrook stream. It stood at one end of the forum or marketplace, enclosed on its other sides by shops and offices.
Twenty years after the first complex containing the basilica had been constructed, work began on a second, far larger basilica and forum on the same site. This took 30 years to complete and involved the removal of surrounding houses and other nearby structures.
The new basilica, which consisted of a large hall with a nave, was three stories high and apparently could be seen from all over the city. At the eastern end of the building’s nave was a raised platform, known as a tribune, where judges would have sat. The new forum’s central rectangular courtyard measured 100 metres by 85 metres in size.
The buildings were variously repaired over the years before being largely destroyed at the start of the 4th century. Speculation is that the destruction was carried out as punishment for London’s support of Carausius, who had declared himself emperor of Britain and northern Gaul in the late 200s. It is believed the eastern end of the basilica was perhaps retained and used as a temple or perhaps even an early church.
Sections of the walls of the basilica and forum apparently still survive in basements around Gracechurch Street today (including apparently in the basement of hairdressers Nicholson and Griffin at 90 Gracechurch Street). The eastern end of the complex now lies under the Leadenhall Market.
Interesting reads on Roman Londinium include Jenny Hall’s Roman London (The Museum of London), and John Morris’ Londinium: London In The Roman Empire. It also worth getting hold of Londinium: A New Map and Guide to Roman London, an invaluable resource for those wanting to come to grips with the city in Roman times.