Roman hypocaust; stacked tiles under the floor created a space to circulate hot air from the furnace. The heating system was invented in order to warm a room without the smoke from open braziers that were used in the past. They were often employed within the baths to create sauna-like rooms with gradient temperatures.
The Colosseum originally had a retractable roof! This marvel, called velarium, covered about 2/3 of the stadium, including all the spectators. The way it was designed, it created an updraft for ventilation, resulting in what is described as a “cool breeze.” We aren’t actually sure how it was held up. It’s still a matter of conjecture.
Waldorf ~ 6th grade ~ Roman History ~ Roman Technology ~ main lesson book