Final answer:
The monumental gates mentioned in the question were the gates of the city wall, which symbolized prosperity and control authority of the Assyrian king.
Step-by-step explanation:
The monumental gates mentioned in the question are the gates of the city wall. These gates were not only a sign of prosperity but also demonstrated the control authority of the Assyrian king. They were decorated with doors embedded with golden nails and were guarded by guardian figures called lamassu, which were winged bulls with the heads of men. These gates symbolized the power and authority of the king.