If you are in a city called Trokdel, look away.

I have posted several questions regarding this city before, but for those who don't know: My party (level 6) recently came into a city called Trokdel, a metropolis that functions primarily as a university for prospective arcane casters. It is divided into eight wedges, one for each school of magic. The entire city is ruled by a council of eight archmages, one for each school of magic.

This was planned to be sort of a pit stop city, but the party decided they wanted to stay in the city for a while, so we are transitioning over to an urban campaign. However, I'm having issues coming up with a way to have a meaningful arc in the city that will still make sense for how it is established.

Only about 5-10% of the city's population has access to more meaningful amounts of magic (the rest are non-magic users or are only level 1-3), but given that the city is one of the oldest cities in the world, it has had a lot of time to advance and has lots of powerful magical nature to it, both aesthetically and functionally. Given that, and on top of there being eight level 18 casters running the place, I am coming up dry on adventures to be had that would let the party have any meaningful-feeling effect. Most ideas that I've come up with I end up scrapping because "Well, if that happened the ______ department would be in charge of solving that".

Basically, how would you suggest I give the party both the personal sense of fulfillment or let them have a reasonable impact on the city (or both) in a city significantly more powerful and more competent than they are?