Topic: Tell me a short, interesting fact about

One fascinating and often overlooked fact about the Roman Empire is that it was one of the first civilizations to extensively use concrete. Romans invented a type of concrete known as opus caementicium, which was a mix of lime, volcanic ash, water, and crushed bricks or tuff (a type of volcanic rock). They used this in extensive building projects, such as the Pantheon, aqueducts, and roads. The Pantheon's dome, for example, stands as the largest unreinforced concrete dome still in existence today – built over 2,000 years ago! The strength and durability of Roman concrete are still under study, and some contemporary builders are even trying to replicate it due to its outstanding properties.