[londons_explore]

The wall is nearly 2000 years old.

It used to be 15 feet high and 10 feet wide. [1]

Nearly everything else that old has fallen down to the foundations. It turns out nature is good at knocking stuff down till it's about a foot high, and then just leaves the footings of all the walls.

Plenty of castles and stuff have 1 foot high walls now.

Also, people steal the stones to build other stuff. But it's more effort to steal stones already buried in the ground.

[1]: https://www.google.com/search?q=how+high+was+hadrians+wall

[lawlessone]

Yeah , people take stones to clear land for farming or to build walls to enclose their farms.

Can't be too mad about it though, the wall was probably relatively new to them

[scott_w]

Also historical preservation was less important to the people at the time when life was, frankly, much harder than it is today. Most well preserved buildings today are the ones that were useful to keep around - for their original or for a new purpose.

[lawlessone]

Roman ruins in post roman Britain must have looked almost magical.