In the comments below it seems that most people don’t know about the existence of Eurostat, and the NUTS2 and NUTS3 maps which they generate. They’re really great, insofar as they give you a fine-grained picture of variation within Europe. Sometimes you see how national boundaries matter a great deal…and in other ways how they don’t.
Above you see a NUTS3 map of purchasing power in relation to the European median. A few things that are salient.
1) France and the United Kingdom exhibit a great deal of wealth concentration around their capital cities.
2) The geographically fragmented and culturally diverse zone from the Low Countries down to Italy’s Po River Valley is seems to be characterized by a large number of economically vibrant cities/regions. The only common variable that I’ve ever been able to point to for this area is that they were under Habsburg hegemony for a very long time.
3) There are zones of poorer nations, such as Spain, which are wealthier than most regions of wealthier regions (e.g., Catalonia is more prosperous than the north of England or rural France across the border).
4) A few of the cities of Eastern Europe seem to be diverging from their host nations.
Below are screenshots of maps I generated from Eurostat, submitted for your comment (remember, don’t be stupid).