Coming up with the theme of "town square": easy.
Coming up with seven city names which contain four or eight of the most common letters: harder.
Fitting those names into blocks of four or eight spaces and starting each name in the upper left square so the words proceed in a clockwise direction: easy.
Arranging those seven blocks in right-to-left symmetry: fairly easy.
Finding words that criss-cross those city names: very difficult.
I'm usually very stinting in giving praise but this is one of the most impressive puzzles I've ever seen. And maybe someday I'll challenge Mister magus to a "useless knowledge" contest.