Paris and Berlin

According to the population estimates for Paris by the National Institute of Statistics and Economic Studies of France, Paris has around 2.1m inhabitants. And according to the population numbers of Berlin by the Federal Statistical Office of Germany, Berlin has around 3.8m inhabitants.

So Berlin is bigger than Paris, almost twice as big, right? And indeed, when looking at the list of cities in the European Union by population within city limits by Wikipedia, Berlin is in first place, and Paris only in fourth. But wait, it's just starting to get interesting.

City of Brussels

The population of the City of Brussels, according to Wikipedia, was 189k in 2021 (no, not B.C.¹). Well, the idea of choosing Brussels as the de facto capital of the European Union was:

As a capital of a small country, it [Brussels] also could not claim to use the presence of institutions to exert pressure on other member states, it being more of a neutral territory between the major European powers.
— "Brussels and the European Union" on Wikipedia

But so small?!

City of London

For the City of London, according to Wikipedia, the population of the City of London is 8,618 — no, not 8.6 million. Literally just 8618 people.

Ok, things are starting to get really unrealistic now. Fair enough, the City of London is just some sort of historic core of London, just as the City of Brussels is. At this point I would like to recommend you to watch the video "The Secret City Inside of London Revealed" by CGP Grey.

City Limits

But back to Paris and Berlin²: The normal city of Paris actually has just 2.1m inhabitants — within city limits. You can inspect the city limits when looking at Paris on Google Maps. Then you can see that Paris is just a small circle in the center of Paris, surrounded by its urban/metropolitan area (Aire urbaine de Paris in French) with 10.5 til 13m inhabitants, depending on the source. For Berlin, however, this is not the case. The city limits define the city pretty good, again as shown by Google Maps. Other capitals with what I would consider to be reasonable city limits are Vienna, Budapest, Rome and Amsterdam, while capitals with city limits that might be too narrow are Copenhagen, Athens and Lisbon.

On the other side, cities in China usually have a broader definition of city limits. For example, the city of Chongqing has an area of 82,403 km² — around twice the size of the Netherlands (41,865 km²), but also almost twice the number of inhabitants. A Wikipedia article³ describes this pretty good:

The Chinese municipality of Chongqing, which is the largest city proper in the world by population, comprises a huge administrative area of 82,403 km², around the size of Austria. However, more than 70% of its 30-million population are actually agricultural workers living in a rural setting.
— "List of largest cities" by Wikipedia

Conclusion

What do we learn from this? Cities in Europe sometimes have legacy city limits and don't update them. So when planning where to perform your next gig, don't just look on the number of inhabitants of a city, but also consider the metropolitan area.