Illyricum is a geographical term that was used by the Romans in the late 1st century BC and the early 1st century AD to describe the new Balkan territory that they were conquering to annex to the Roman Empire. It included the lands which extended from the western boundary of modern Greece to the Alps on the west and from the Danube River on the north to the Adriatic Sea. Two of the best known rulers of the Empire, Julius Caesar and the first Emperor Augustus are associated with the annexation of Illyricum. Towards the end of the Empire, in the 4th century, Illyricum again gains currency as an administrative term, first in the reorganization of the provinces under the Emperor Diocletian and later as the Prefecture of Illyricum under the Emperor Constantine the Great. Because they were born in this area, usually to military families, Diocletian and Constantine along with some of their predecessors are known as “the Illyrian emperors”. Today the term Illyricum is used to designate the modern countries proposed for the West Balkan Extension of the Roman Emperors and Danube Wine Route.