How did hadrian protect the roman empires border

Hadrian focused his reign in establishing frontiers of the roman empire that were easy to defend. In the ones that were harder to defend, he focused on building several kind of fortifications like pits, embankments, watchtowers, and palisades.

The most famous one was a wall in the province of Britain, nowadays known as "The Hadrian's wall", which prevented northern invasions from barbarians.