About the Alley With the Street Light
In the Lesser Quarter is the Vinarna Certovka, the alley that claims to be the narrowest in the world, and in the Czech Republic, but might only be the narrowest in Prague.
It is hard to be entirely accurate, but the street is less than 20 inches in width (about 50 centimeters), and really is a narrow alley. The alley is so narrow in fact, that no more than one adult can walk through it at once. This is why the city of Prague has put in pedestrian stop lights, and has turned this street into a tourist destination - the stop light is meant to alleviate the traffic when people come to the alley from both directions - you can only walk through when you have a green light.