There's a new book about Japan called Drainspotting. It's based on a blog by Remo Camerota, and features lots of colorful, beautiful photos of manhole covers. Manhole covers are art mediums used by municipalities to show off regional pride in things like local landmarks, region-specific art styles, and native plants.
In Japan, modern sewer systems began to appearduring the late 19th century, though evidence of sewage systems in the country dates back to over 2,000 years ago. Foreign engineers introduced the Japanese to modern, underground sewer systems with above ground access points called manhoru (manholes). At that time, manhole covers utilized the geometric designs similar to those used in other countries. In the 1980s, as communities outside of Japan's major cities were slated to receive new sewer systems these public works projects were met with resistance, until one dedicated bureaucrat solved the problem by devising a way to make these mostly invisible systems aesthetically appreciated aboveground: customized manhole covers.Drainspotting: Japanese Manhole Covers from Mark Batty Publisher