Final answer:
The largest building in Persepolis is the Apadana, an audience hall covering around 1,000 square meters and supported by 72 columns that were 24 meters high each.
Step-by-step explanation:
The largest building of the complex in Persepolis, Iran, is the Apadana. The Apādana was likely an audience hall with an associated portico, massively built, having a hypostyle plan. This is indicated by the massive footprint it covers, approximately 1,000 square meters, and supported by substantial columns that stood 24 meters high. Originally, there were 72 columns, but only 14 remain standing today. These columns were adorned with column capitals in the form of animals that symbolized royal authority, such as twin-headed bulls, eagles, or lions.