Actually more than a century older than the Aurelian Walls, Hadrian's Wall runs across the entire length of England. It was built by its namesake emperor and marked the northernmost point of the Roman Empire in Great Britain. Stretching for 84 miles from the east to west coasts, parts of the wall have been broken down or eroded over the years. Sections still remain largely intact however. A trail runs for almost the entire length of the wall and much of the surrounding area is undeveloped. This makes it easy to picture what the structure must have looked like when it was built. The trail is broken down into six walkable sections, making a weeklong trek possible.