This stone relief shows the struggle between a bull and a lion. This is a very ancient Iranian motif, known from the fourth millennium BC.

It symbolizes (probably) eternity and seems an excellent theme for this place. The people who visited the Apadana offered tribute to the great king who was supposed to keep the continuation of the empire.

Also, a symbol of Zoroastrian Nowruz - in day of a spring equinox power of eternally fighting bull (personifying the Moon and Earth), and a lion (personifying the Sun and Spring), are equal.