So "rynek" can be used in an abstract sense? Like, the market for computers, for example?
Edit: In fact, that would be my main interpretation. If it was about a real 'market square', I'm not sure if I would use 'ten'.
If we were to interpret 'rynek' as a place, it would be a 'market square', not just any square. And that's accepted :)
If 'this square is changing fast' is accepted, then so should 'this square is quickly changing' be.
Well, 'square' wasn't so far, but in the meantime we decided to accept it... so added here. "is quickly changing" worked already.