What raids a city: the one question the snapshot was scraped to answer,
since the wiki writes raids on one page per city. The same rows are
reachable as /raids?filter[city]=.

Four raids happen somewhere the game does not call a city at all —
Gnomebase and the Plains of Havoc among them — so they keep the
snapshot's own word for where in city and can only be found from
/raids. A city nothing attacks answers an empty page rather than a 404.