I'm European. They exist. The government doesn't exactly like acknowledging them. Since it's like Obama talking about, I don't know, Compton? I hear things are better there now, so that's probably not the best example. It's not flattering, and it raises uncomfortable questions about race / religious relations in your country.
Molenbeek in Belgium is a good example. It's a municipality of Brussels which has become known as "Jihadi central", because so many terrorists have come from it (Paris, Madrid, that market shooting, etc). Last week the Belgian home minister outright admitted that the authorities have no control over it. Hence why they basically had to send in army to get the suspects.
In France they have what they call "sensitive urban zones". It's basically a polite way of saying ghetto.
Similar situation in parts of Britain. There was some hysteria about "Sharia zones" a while back. That's actually not inaccurate. There isn't a literal Sharia court involved (usually), but you will run into problems if you don't follow the understood rules in certain neighborhoods.