It occurs to me that, if Alexander (He wasn't entirely good!) hadn't destroyed it--had it burnt, actually--we should probably have to include Persepolis

among those ravishingly beautiful architectural monuments that we--or somebody at the UN decides are to be preserved forever in situ, unchanged, regardless of their purpose and function in the real world. No doubt. They say Persepolis was lovely. 

But my favorite chose persane is the water garden, as at the al-Hambra, and as in Kashmir, which these preternaturally clever Persians invented, using only gravity flow, to  cool and embellish the stark, hot aridity of geographical Persia. The very word Paradise is, I think, a Persian word, and means something like "enclosed garden w/fountain."

Gotta say I love this picture of this particular garden--if you click on it it expands--which is very old and very lovely.