Spectacle · Roman Empire Daily
The Colosseum had a huge fabric awning, the velarium, rigged by sailors to shade the crowd from the sun.
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A system of masts and ropes let crews unfurl the velarium over the seating. Detachments of sailors, expert with rigging, were used to operate it.
Source: Pliny the Elder, 'Natural History,' 19.23–24; standard surveys.