 Romanization in the area was extremely slow, even though eventually the native language gave way, and the people in Cerdanya ended up speaking Catalan, a language derived from Latin.At the end of the Roman Empire, Julia Lybica entered a period of decadence, and lost much of its importance.It is around this time that the town of La Seu d'Urgell (in Catalonia, but outside of Cerdanya) started to replace Julia Lybica as the main center of population in that area of northern Catalonia, and in the 6th century when the diocese (bishopric) of Urgell was founded, Cerdanya was inside its limits.