Enlil Lines. Basically, any base or camp or operating area specific to a certain unit of the army could be called Lines. So if one considered the academy as a whole as an army base, then the lines were the bases of specific groups within that army base. Since the students were divided into four battalions, the base for each battalion was called a line.
The Enlil line felt small and big at the same time. There was a dedicated mess building, which was easily identifiable because it read 'Mess' right in front of it. There were a number of barracks buildings which were standardised, single story buildings, and a number of larger buildings that Nero could not identify the purpose of.
