Commentary Par VI 2-3

The Eagle, symbol of the Roman Empire, originally, with Aeneas, followed the course of the heavens, encircling the earth from east to west.  Subsequently, it moved from west (Italy) to east (Constantinople), where Constantine had transferred the seat of empire in 330, and where Justinian governed from 527 until 565.

Aeneas's taking Lavinia to wife, not recounted in the Aeneid, is the only Virgilian detail that is reprocessed in Justinian's epic narrative.