Borders of the Roman Empire

[2] The Sasanians succeeded the Parthians in 224–226 and were recognised as one of the leading world powers alongside its neighbouring arch-rival the Roman (Byzantine) Empire for a period of more than 400 years.

At the greatest extent of the Empire, the southern border lay along the deserts of Arabia in the Egyptian region and the Sahara in North Africa, which represented a natural barrier against expansion.

However, the Romans controlled the Nile many kilometres into Africa up to Syena, Berenice, Hyerasykaminos and even Qasr Ibrim (the southernmost of all), near the modern border between Egypt and Sudan.

[3] In the south of Mauritania Tingitana Romans made a limes in the third century, just north of the area of actual Casablanca near Sala and stretching to Volubilis.

Septimius Severus expanded the "Limes Tripolitanus" dramatically, even briefly holding a military presence in the Garamantian capital Garama in AD 203.

Roman Empire at its greatest extent in AD 117
Vassal states
Map of the Roman Empire in 125 during the reign of emperor Hadrian
The limes that protected the Empire from German raids.
Location of Hadrian's Wall and the Antonine Wall in Scotland and Northern England.
Map of Limes in Slovakia, Hungary, Croatia and Serbia
Limes Africanus under Septimius Severus (The frontier of Roman Africa (dark tan) in the late 2nd century AD: Septimius Severus expanded the Limes Tripolitanus dramatically (medium tan), even briefly holding a military presence (light tan) in the Garamantian capital Garama in 203)
Tabula Peutingeriana