When did Barcelona start?

There are two main legends as to Barcelona's founding. One says that it was built by Hercules and the other says that it was built by the Carthaginians as an outpost. However, the city only truly developed during the Roman Period when the Romans mapped it out in 15 BCE.

Barcelona only became a large and important city some centuries later since it sat in the shadow of "Tarraco" which is now the city of Tarragona.