Who did Hadrian's Wall, a massive defensive structure, primarily aim to keep out?

Hadrian's Wall, a truly impressive feat of Roman engineering, wasn't just a random construction project; it served a very specific purpose. Think of it as a physical manifestation of the Roman Empire's boundary in Britain around 122 AD. The Romans had conquered much of the island, but the area north of what is now northern England proved difficult to control. The people inhabiting that region were known as the Picts. Now, the Picts were a tribal confederation known for their fierce independence and, interestingly, their practice of body painting or tattooing, hence the hint about 'picture people'. They frequently raided Roman settlements to the south. Hadrian's Wall, stretching roughly 73 miles, was built to defend against these raids and to control movement in and out of Roman territory. The Irish were across the Irish Sea, the Welsh were to the west, and the Vikings came much later, so Hadrian's Wall was primarily a barrier against the Picts.