Just an aside, the Colosseum, long held up as an example of superior Roman concrete construction, is mostly brick as well...which I found infinitely surprising

Just an aside, the Colosseum, long held up as an example of superior Roman concrete construction, is mostly brick as well...which I found infinitely surprising when I finally had a chance to visit it. [1] Here's a walk around the structure [2], it's virtually all brick. [1] [2] https://www.youtube.com/watch?v=uWkct044pFU https://www.youtube.com/watch?v=uWkct044pFU