[nomel]

With "pockets of", I read this

> It also shows that pockets of architectural knowledge rapidly advanced and then receded all across the known world.

as "individual pockets, all around the world, advanced and receded."

[ummonk]

Oh, you're right. My objection was based on my own misinterpretation of "pockets" as referring to time periods and/or specific architectural knowledge rather than to particular locations.