Take a Tour of a Japanese Manhole Factory Where Neighborhoods Create Their Own Designs. In most countries, the design of manhole covers is scarcely given a second thought other than the basics of material and a generic pattern resulting in drab metal circles with a purely utilitarian function. But after World War II, city planners in Japan proposed the idea of allowing each local municipality to design their own manhole cover as part of an effort to raise awareness for costly sewage projects. Designs would reflect local industry, culture, and history. The result was a huge success, and now over 19,000 manhole cover designs can be found embedded across 95% of all municipalities in Japan.