Looking at the currently well known (to a USA-ian) European Cities, some of them become significant cities earlier than others. For example, even in a TL with a Avignon Papacy and a strong Sicily (vs a unified Po Valley), Rome would still be well known.
It appears, however that the cities that can be made relatively insignificant with PODs as late as the 1700s. With no-miracle of Brandenburg and a Prussia Stomping, Berlin could easily be in the second tier of German cities, well behind Hamburg and Hanover. (Note, as far as I'm concerned OTL from 1500 to 1900 is a BerlinWank)
Moscow is somewhat more difficult, I'm not sure simply leaving the Capital in St. Petersburg works, I think it would still be more important/well known than Volgagrad/Stalingrad. Does every real option here go back to a surviving Polish/Lithuanian Commonwealth?(Note, even in a Nazis sweep all the way to the Urals, it would still be well known)
Are there any other Significant European Cities whose rise to being among the first tier (or high second tier) can be aborted with post 1500 PODs.