Applications in Various Industries
According to Atlas Obscura, manholes date back to the mid-19th century when cities around the world were building underground sewage systems. Engineers realized that they needed to access the sewer systems for the purpose of inspecting the pipes during normal maintenance. Consequently, cities began digging access holes that could accommodate a human (as these workers were typically men, the access points were called manholes) and these became the portals through which engineers or inspectors could crawl to investigate the pipes.