1 of the cities which your parents will definitely like is Ljubljana. This amazing city is repeatedly called the second Prague, because of its amazing architecture. Nevertheless, it is much less busy and all of those incredible places and buildings can be seen with no lines (take a look). Moreover, even though you would most probably become such trip from the Ljubljana (as there are plenty of cheap flights to Ljubljana), there are also many other places which worth to see in Slovenia. E.g., in this small country you can see charming Alps and gorgeous lake. And all of it is located in less than two hours journey from Lubljana. Doesn’t it sound marvelous? Your parents will absolutely love it!
Other place which may be a great idea for a trip with beloved parents is Chicago. The generation of our parents very frequently sees America as a rich and unavailable country. Actually, it makes sense if we think that most of people in their generation were travelling to Chicago not as visitors, but in order to find a job.