Characteristic quality of articles about ancient city (4)

I believe the answer is:
aura
'characteristic quality' is the definition.
'aura' can be an answer for 'quality' (aura is a kind of quality). I am unsure of the 'characteristic' bit.
'articles about ancient city' is the wordplay.
'articles' becomes 'aa' (the English indefinite article written twice).
'about' means one lot of letters goes inside another.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'aa' going around 'ur' is 'AURA'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for aura that I've seen before include "Mystic air" , "Indiscernible quality" , "Perception of distinctive personality" , "Supposed emanation surrounding the body" , "Intangible something around a person" .)
