The Via Egnatia was an important part of the Roman road network mainly because it connected Rome with Constantinople (modern day Istanbul). It became a lifeline between the Western and Eastern parts of the huge Empire.
The need for such a road arose with the Roman expansion towards the east. At the time before the road existed, there was no infrastructure in the newly conquered provinces and communication with Rome was hard.
According to some written accounts, the construction of the road began in 145 BC, under the supervision of Gnaeus Egnatius, the newly appointed governor of the province of Macedonia. The road took the name of its builder.
Part of the Via Egnatia in Albania. Author: Albinfo CC BY-SA 4.0
Via Egnatia begins on the eastern shore of the Adriatic Sea, near the ancient port of Dyrrachium (modern-day Durres, Albania) and it lays directly opposite Brindisi, at the end of Via Appia. Via Appia was one of the oldest and most prestigious roads in the ancient Roman Empire which connected Rome to Brindisi, on the western shore of the Adriatic.
The road then followed the River Genussus (Shkumbin) and went over Jablanica Mountain, from where it descended to the shores of Lake Lychnitis (today named Lake Sevan) and it passed near the ancient town of Lychnidos (modern-day Ohrid, Macedonia).
From here, the road turns south and goes over a few high mountain passes before continuing east, passing through Pella (the ancient capital of the kingdom of Alexander the Great). Then Via Egnatia reaches the northern coastline of the Aegean Sea at the city of Thessalonica. From Thessalonica, the road went all the way to Constantinople (Istanbul). This route is a total distance of around 695 miles.