I don't know for now, i'm really open to any suggestion, and haven't started thinking in more details but i have a few ideas :)
For example, it could be a multiplayer game in which you have to build a city together. In competition or cooperation ? i don't know. to what goal ? to prove what point ? i don't know either.
It could also be a a cooperative game in which you have to adapt to a city slowly building itself, and score as many points as possible.
I was also thinking maybe it could be a Castle of Cards game with the twist of having some cards require you put them in specific places, or give you more points.
There was also this game in which you had to build a path from point A to point B using tiles looking like spaghetti plates. The whole game revolved around the fact that each piece could be an obstacle as well as a step forward depending on the side you approached it from. Something similar might be possible, but with a city building itself, allowing fluxes of merchants, citizens etc... to go around the city.
Really, idk, i'm just throwing ideas around ^^ what do you think an architectural game could be ? :p