My proposal is to have no geographic sub-districts to any polity. Everyone in a city should be free to vote for all candidates for city council, everyone in a region should be free to vote for all candidates for the regional assembly, everyone in a country should be free to vote for all candidates for the National Assembly. But if you really wanted to rescue some unique neighborhood, my suggestion is that you do so directly, without trying to achieve the effect as the accidental side effect of an unrelated architectural decision. The neighborhood with the unique culture has voters who will express their interests in city, regional, and national elections, and that should be enough, but if you felt strongly that this unique neighborhood deserves additional protections, then my suggestion is that you pursue that goal directly. Incorporating that neighborhood as its own independent city would be a way of achieving that goal.

About this:

"What do cities have to do with congressional boundaries? Districts span cities."

My point is that districts should not exist.