The Roman Colosseum had a Retractable Roof
Almost everyone knows about the Roman Colosseum- but not many people know that it actually had a retractable roof! The retractable fabric roof, called a "velarium", not only protected spectators from the elements, but actually created a ventilation upwards, bringing spectators a cool breeze. Pretty impressive stuff.
I upvoted You
Nice @backdrive
Shot you an Upvote :)