Europe in late September

London, Amsterdam, Palermo.

Sardinia and Corsica.

Alsace, Rhine River Valley, Moselle River Valley, Loire

Paris. And then there's...Paris. And again...there's Paris. Or maybe London which is good any time too!

Rome is the best city in Europe for tourists. Autumn is a good time to visit. For a region, either Yorkshire, England or Andalucia, Spain are best. Or Flanders.

At least those are my picks, but I wonder if any of these replies are helping, since you've not identified any likes/dislikes.

Vienna and Graz/Styria

No place in Europe should be too hot, too cold, too wet, nor closed-up during this time. Some ferries in Croatia and Greece might operate a mid-season (not off-season) schedule.

This question is so general, there are no bad choices.

Shoulder season is great in general. Maybe not so much if you specifically want to do a lot of swimming in the Baltic Sea, but without more specifics, this question is basically asking "where in Europe do you like?"

For how long? From mid Sept to mid-Oct, ie 30 days, I would pick Paris, Vienna, London, or, Alsace-Lorraine and eastern Germany.

Anywhere with a wine industry. Rhine/Moselle Valleys, Burgundy, Bordeaux, Alsace, Champagne, Rioja, Tuscany. September is when the grapes are harvested and there are lots of local festivals.

Sorry for my ignorance. Maybe I should narrow it down. Choosing between Lisbon and Portugal, Bulgaria and Sofia, Belgrade, and Budapest. Also anywhere in Eastern Europe. Been to Paris, London, and Germany.

I would go to Portugal!

If it is"anywhere in eastern Europe," I would choose Warsaw, Gdansk and Budapest...all very easy to visit in 3-4 weeks.

Sorry for my ignorance. Maybe I should narrow it down. Choosing between Lisbon and Portugal, Bulgaria and Sofia, Belgrade, and Budapest. Also anywhere in Eastern Europe. Been to Paris, London, and Germany.

YES!

All of the above. Its my favorite time of year to be in Eastern Europe. You will find me in Budapest in October, like almost every October. I enjoy Sofia a lot too. Much to see within an hour or two of Sofia. And now non-stop discount airline service from Sofia to Budapest. Belgrade? I wasn't as impressed with Belgrade; but interesting.

September is my favourite time to visit Portugal. Better food generally than say Poland.

I haven't been to Portugal since the early 1990s, and I'm in Poland right now, so this is not an apples-to-apples comparison. Also, I do not go to fancy restaurants, so I have no idea how they compare from country to country; I look for middle-class places.

I think without any sort of research you are probably more likely to end up with mediocre food in non-touristy parts of Poland than in similar areas of Portugal--though my reaction is perhaps related to my not being a big meat-and-potatoes fan.

However, there's some really good food in Poland if you ask around and do a bit of research. The best Thai restaurant I've been to in my life (haven't been to Thailand) was in Warsaw, and the best Greek restaurant (i have been to Greece three times) was in Poznan. As it hapoens, both of those were lucky discoveries of my own, based on reading their menus. However, that brings up a problem of traveling in the former iron curtain countries in general (not so much Budapest, but in many other places): all too often there is no menu posted outside--not even in the local language. I'm sure I've walked past some great places but eliminated them from consideration because without a menu, I had no idea whether they served anything other than sandwiches/salads, or whether I'd be able to put together a healthy meal (i.e., whether there would be non-starchy cooked vegetables available). So I agree that it is taking just a bit more work for me to find what I want in Poland.

This is a great time to visit Europe, so really can't go wrong anywhere that you choose. For me, I enjoy Southern Italy (especially Rome) and Andalucia, Spain. You still get great weather, but not quite so warm.