Tarraconesis (Hispania)

By the end of the third century after Christ, the emperor Diocletian made the final reorganization of Spain under Roman rule. He divided the province of Tarraconensis into three additional provinces: Cartaginensis, Gallaetia, and Tarraconensis. During this period trade began to decline. The gold and silver had been drained from the eastern coast, and the government responded by attempting to regulate wages and prices. Individuals were deprived of the freedom of movement and the right to change their occupations.

...but couldn't find any figures for Hispanian city populations after the fall of the Roman Empire (looked specifically for Tarragona/Tarraco and Barcelona/Barcino)

_{*Lunatic*, n.
One whose delusions are out of fashion.}