The primary material used in building the Colosseum was travertine limestone, a type of stone quarried from Tibur (modern-day Tivoli) near Rome. It was used for the main pillars, walls, and structural elements. Additionally, tuff, a volcanic rock, was used for other columns and radial walls. Roman concrete, invented by the Romans, was also a key material, particularly for the vaulted arches and foundations.
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