Ever since I began following concepts and designs for this blog, I've noticed that they seem to fall into several distinct categories. You have the completely outlandish dreams that are unlikely to ever work in the real world. Then there's the practical and possible concepts that could actually help humanity based upon current technology. And finally there's the concepts that seem like they're from the deep past as opposed to the distant future.
The Map-Hole concept designed by Jiae Kwon falls decidely in category # 3. This concept might have been revolutionary 50 years ago, but in a world where you can get turn-by-turn directions and full maps on your mobile phone, this concept is really late to the game.
The Map Hole is a pretty simple urban navigation tool that places bearings and travel times to popular destinations on manhole covers. I suppose the thinking goes that manhole covers are an existing template that could easily be used to provide a second function. Of course, as several Yanko commentors point out, manhole covers tend to be in the middle of the street where you probably shouldn't be standing around figuring out which way to walk. And then there's the issue of what happens when the cover is removed and placed back completely at random, rendering the directions more harm than good.
Certainly an interesting idea, but it doesn't seem that practical or necessary in today's world. Those that need this type of navigation could rely on inexpensive and easy-to-use GPS-based devices and apps, whereas installing Map Holes into any given city would create a rather imposing public expense--too little gained to justify the costs.