If Rome is called the eternal city, I would say that Brussels is the ephemeral one..
Be it for a couple of months, years or even decades, there is definitely a lot of people just passing by. As awward as it may seem, this city is not a destination in itself, it's just a way through to somewhere or something. Even if that something is a work with the European or other international institutions, likely to be placed here.
And there again, we cannot say that all the ways lead to Brussels. But we could say that all the ways pass by, making of this intriguing city an “auberge” in the croosroad of many, maybe even too many, life paths.