Most scholars (like this one) believe that Velia is the ancient name of the ridge that connects the Palatine and the Esquiline; it is one of the eight places mentioned in the list known as Septimontium. In an article on the historical topography of the Velia, originally in the Transactions of the American Philological Association, H.F. Rebert shows that the name Velia in fact refers to a slightly different area, to the west of what is now believed to be the Velia. The article has been made available now by LacusCurtius‘ Bill Thayer, and you can find it here.