Four strange places to see London's Roman Wall

On the subject of walls... Cortez reported seeing a wall blocking off an entire valley on his way to Tenochtitlan. One source reported the wall was 6 miles long, and yet it seems to have disappeared without a trace. And yet, Both the London Wall and Hadrian's Wall, though much older still have surviving ruins to this day.

I wonder if they exaggerated things to make their conquest seem even more impressive

Frankly, they didn't much need to do so. The empire they encountered was epic and amazing.

Cut stone is worth stealing to make new buildings.

In 1491 the point is made that the Inca believed that they had been beaten by superior gods and so they bowed out. But he doesn’t really talk about what happened to the Aztecs. You steal stone from structures you don’t care about anymore.

Didn’t Mexico see more intensive colonization? Settlers would care less about existing structures. Maybe the Spaniards built missions out of the wall.