Lutetia was increasingly under attack by Germanic tribes.
The Parisians joined small islands on the Seine together to form one big island - today's Ile de la Cité.
Most of the Roman buildings on the Left Bank were broken down and their stones used as fortifications.
A famous barbarian invasion occurred in 451 AD, when Attila the Hun and his army advanced on Paris.
The legend goes that a majority of Parisians tried to flee the city but a local noblewoman, Genevieve, persuaded them to stay.
The Huns diverted their attack to Orleans.
Genevieve became Sainte Geneviève, the patron saint of Paris.
The barbarian attacks culminated in the collapse of the Western Roman Empire.
Clovis, who became king of the Franks, made Paris his capital.
He converted to Christianity and built an abbey on the hill, the Abbaye Sainte Geneviève - part of which is still visible in today's Lycée Henri IV - where he was buried with Sainte Geneviève.
The neighbourhood is full of references to this period : rue Clovis, rue Clothilde (Clovis' wife), rue Clotaire (their son), the Bibliotheque Sainte Geneviève, the Montagne Sainte Geneviève...
The Frankish Kingdom became the largest kingdom in Western Europe.
The name Clovis gave rise to the name Louis - the name of 18 French kings.
The word Frank gave rise to the name France!