Gate to the gap

This skinny door enables access to the space between two adjacent buildings. (The sign says "no unauthorized people allowed.") In contrast to a city like Manhattan, buildings in Tokyo rarely share walls. The result is a city full of gaps. This particular gap, though, is pretty wide in comparison to most, which so are often so narrow that physical access to them is impossible. They are great places for all sorts of refuse to build up over the years. Someone should come up with a type of architectural dental floss to clean these spaces.