Two things I found very impressive about ancient architecture of Iran:
1) buildings were often built in four parts, and use of the parts were rotated according to season. the winter section was smaller and more tightly sealed, easier to heat. the hot weather sections were strategically placed to avoid the worst of the sun during the active hours of the day.
2)they used windcatchers-cleverly placed holes in the upper walls and ceiling that would seize the breeze and optimize the circulation of cooler air.
3)ok, three things. the longevity of the buildings.