Final answer:
The columns of the Hall of a Hundred Columns in Persepolis were made of gray limestone and mud-brick.
Step-by-step explanation:
The columns of the Hall of a Hundred Columns in Persepolis were made of gray limestone and mud-brick. The Persians used the abundant gray limestone from the surrounding area and combined it with mud-brick, which was common in the Mesopotamian area. This combination of materials was used to construct the columns of the Hall of a Hundred Columns.