I suggest a travel from Tehran Capital City (due to his best Musuems) then if you wanna some religious place, travel to Qom Secound Holliest place in Iran (of course this is selective and you can delet this city because this city is also center of Mollas in Iran) then to Kashan a safe place near Tehran with all condition of Desert cities of Iran (this city have very nice, old and beutifull houses), then go to Isfahan ,Capital of Safavid, very beautifull mousques in Imam Square and Vank Church is very nice place, then if you really wanna to see a fire temple must go to Yazd, there is a real fire temple (If I understood you and you wanna to see a real and working fire temple but if you wanna to see ruins of a fire temple delet this city and go from Isfahan to Shiraz), OK now we reached Shiraz. There was inside city only some Iranian Garden that you saw best of them in Kashan (Fin Garden), so go outside of city about 60 kilometers of city Pasargad and about 30 KMs Perspolis ruins, in secound one you can find what do you came Iran for, one of Achemidians Capital city and best of them, also in 80 kMs of Shiraz Sasanid city of Kazeron.
so this is my suggeting rout. came from Tehran to southern part and there was an Airline to Doubai from Shiraz and then where ever you wanna to go