It is a separate city, that is surrounded by Detroit except for one small portion touching Hamtramck which is also surrounded by Detroit: https://en.wikipedia.o

It is a separate city, that is surrounded by Detroit except for one small portion touching Hamtramck which is also surrounded by Detroit: https://en.wikipedia.org/wiki/Highland_Park,_Michigan https://en.wikipedia.org/wiki/Highland_Park,_Michigan It's not terribly uncommon for a city like Detroit to annex surrounding towns and cities, but some of them hold out, which looks like is what happened here.