As with any country, people traveling to Iran for the first time and not knowing much about the country want to know which places are “must see” and which places they can skip. Since Iran is a very large country, about as twice a big as France and Germany combined or 2 1/2 times the size of Texas. This means there is a lot of ground to cover and for most travelers, choices will have to be made.
We recommend that if you arrive by air in Tehran, you do not spend too much time there. Unless you are particularly interested in museums and want to devote a lot of time visiting them, Tehran is a large, traffic-jammed city.
You can take a domestic flight to Shiraz, about 1 hour, and start your trip from there, working your way back north to Tehran for your flight home. That is the way most of our tours work.
As far as which cities you must see – Shiraz, which includes Persepolis and other ancient sites; Yazd, for Zoroastrian culture and, of course, Isfahan. the most popular tourist city in Iran.
Of course, there is a lot more to see, depending how much time you have. But those three cities, mentioned above, are the “must sees”. You can forget about places mentioned in many travel chat rooms, such as Masouleh, unless you have a lot of extra time. It is probably not worth the trouble of getting there for most tourists.