My understanding is that you use dans when referring to a specific place (which is preceded by an article) while en is used to refer to a more general, abstract or symbolic place (no article).
Je suis dans la classe. vs Il est en classe.
I’m in the classroom. vs He is in class.
But then the following example is given that confuses me:
Je vais en ville - I’m going TO town. Why is it not written using “à?”
Thank you for any help!