OCD(4) p.129; Barrington Atlas map 19 grid F4. (NB: the present gloss makes it clear that this is not the smaller Aquileia in Germany: ib. map 12 grid D4.) See also alpha 938.
Aquileia has a strategic location at the head of the Adriatic Sea, controlling roads over the Alps. Gauls occupied the site in 186 BC. The Romans ejected them and founded a Latin colony in 181 BC (Livy 39.22, 54; 40.34). Aquileia was a large military, commercial, and industrial city under the empire. The amber trade was especially important (Strabo 4.207f.; 5.214). A Christian church council was held there in 381 with Ambrose presiding. Attila sacked the city in 452 but did not destroy it. Aquileia's bishop became a patriarch in the 6th century and the patriarchate continued influential through the middle ages. Information on councils held at Aquileia may be found on the Catholic Encyclopedia web site (web address 1). Excavations of the basilica have revealed remarkable 4th-century floor mosaics (see UNESCO World Heritage Site page at web address 2).
[2] Stephanus of Byzantium s.v. gives the ethnikon as *\Akulh/ios, but the Suda's form is the norm in (e.g.) Herodian's History.