Livy said of Alba Longa that it was founded by Ascanius to relieve crowding at Lavinium. He placed it at the foot of the Alban Mount and said that it took its name from being extended along a ridge. Dionysius of Halicarnassus repeated the story, but added that Ascanius, following an oracle given to his father, collected other Latin populations as well. Noting that Latin: alba means "white" and Latin: longa means "long", he translated the name into the Greek language as "long white town". Dionysius placed the town between the Alban Mount and the Alban Lake, thus beginning a long controversy about its location.
Since the 16th century, the site has been at various times identified as that of the Convent of St. Paul at Palazzola near Albano, Coste Caselle near Marino, and Castel Gandolfo. The last named of these places in fact occupies the site of the Villa of Domitian which, according to Juvenal, was situated on the arx of Alba.
Archaeological data show the existence of a string of villages in the Iron Age, each with its own necropolis, along the south-western shore of Lake Albano. At the time of being destroyed by Rome, these villages must have still been in a pre-urban phase, beginning to group around a centre which may well have been Castel Gandolfo, whose significantly larger necropolis suggests a larger town.
In the later republican period the territory of Alba (the Ager Albanus) was settled once again with many residential villas, which are mentioned in ancient literature and of which remains are extant.