That's a narrow alley!!! And do you know what to find at the end of it? Me neither... But for sure not just a wall.
I enjoyed to lose myself in the deeper area of the Hutong of Gulou and I always tried to not cross the privacy line of people living there. I've been to some areas where I meet some people who simply asked be to turn back. They were not used to see "Laowai" around their houses. This is China.