Concept:
The most important architecture of the Achaemenid era is the magnificent palace complex of Persepolis (literally means"city of persians") or Parse, was the ceremonial capital of the Achaemenid Empire and it is located at the foothills of Mount Rahmat, Marvdasht, Shiraz-Iran.
At the entrance (the gate of all nations, Through this gate would pass all the representatives of the various conquered territories as they came to pay homage to the Achaemenid emperors), figures in the form of winged cows with human heads is visible, which are called Lamassu.
(The Lamassu is a mythical creature. 
These towering creatures were over four meters tall and depicted a beast with the body of a bull or lion, the head of a man, and the wings of an eagle.) The Lamassu served as the symbolic protector of a king palace. Its ears used to cover with the rings of power.