The zone takes its name from a curious event that occurred to Emperor Constantine the Great, when, during the Battle of Saxa Rubra (312), the labarum fell out of his hand.

According to another theory, the name Labaro derives from a medieval interpretation of the Latin word Rubrae (which became Lubrae and then Labarum).

To the north, the zone borders with Zona Prima Porta (Z. LVIII), from which is separated by the stretch of Via della Giustiniana between the river Cremera and the Fosso di Monte Oliviero, then by the stream itself up to the Tiber.

Eastward, it borders with Zona Marcigliana (Z. III), whose boundary is outlined by the river Tiber, up to the Ponte di Castel Giubileo.

Streets and squares of Labaro are generally named after towns of Friuli-Venezia Giulia and Lombardy or after Italian artists and historians.