Officially? French in the South, Flemish in the North, mixed French/Flemish in Brussels and in the East a small part German... but most of us speak and understand English
did I mention that they all have their own government + a federal government on top of that + a European government... and we also have a king and his expensive family.
You understand now that we have about the highest tax-rates in the world?
I see that I forgot to mention the province-level, a government placed between the city and the regional governments (regions: Wallonie, Flanders, Brussels and the German cantons.
and all that in a country with about the same amount of inhabitants as a (middle-sized) city in the States...