“... a reason for the location of Hadrian’s Wall was partly due to a geological fault zone that resulted in a natural stone facing several meters high and unscaleable in several places.”
Yes, according to what I’ve seen or read. The Romans were not dumb, and surveyed carefully to choose the route for the wall that would give them the maximum elevation in the area.
Also, from documentaries I’ve seen:
* Apart from its semi-practical use (it wouldn’t stop invaders), it was also simply a “make-work” project. Hadrian was a firm believer that idle soldiers were trouble. If it wasn’t the wall, it would have been something equally fascinating they would have been assigned to build, just to keep them busy.
* It was more for funneling people through the gates, to collect taxes, than for being a military bulwark.
* Hadrian was a hands-on kind of emperor. He came to inspect the work. He decided the wall needed to be wider than it was. All of the wall that had been built so far had to be widened — and this did not just mean adding width to what was standing, it meant widening the foundations themselves. What a pain!
* Then the Antoinine Wall was built by a later emperor, farther north, rendering Hadrian’s wall irrelevant.
* Then the Romans abandoned England and Scotland altogether, and the soldiers tossed their rolled-up letter scrolls into trash heaps, wells, and fire pits. Wisely, archaeologists did not try to unroll them until technology advanced enough for them to use X-rays and UV light to read them, before the unrolling destroyed the fragile documents. They give amazing insights into the kinds of things soldiers would write home about, and the kinds of letters they would receive in turn. Yes, there are things written home like “send more underwear”! Real, human stuff.
* The archaeologists also have come up with literally more than a million discarded shoes. The soldiers went through a lot of shoes. I wish they’d put some of those shoes up on eBay.
“Hadrian was a firm believer that idle soldiers were trouble.” And that tradition/belief has continued on through the ages and is the reason why you may have heard stories from your father or grandfather about having to paint the rocks lining the walkways in front of the orderly room and/or barracks.