Automated door technology appeared in 1931 and was considered one of the signs of the “modern” age. Yet, the world had already seen this technology back in 1 AD. So how did it work? If you wanted to open the door, a fire would need to be lit to generate heat, causing an atmospheric build-up in brass vessels. This vessel would then pump water in holding containers, and these functions would act as weights to open the door. Think of it as a hydraulic system. Unfortunately, the doors were not that practical and not as popular as the modern doors you have around your city. The ancient doors took hours to open, and the process was hard to stop once it started. So, this probably meant that you only opened your doors once a day.