The closest street in Sweden

Yes, it is in Gamla Stan and boasts the smallest street in Stockholm, Sweden and one of the closest in Europe. How do you find it? If you walk to the end of the street Västerlånggatan can find it without problems, since it is the latter perpendicular to it, just before a square. In its narrowest is only 90 centimeters. The strange thing is that you can only pass in single file.