MB4 197b: Width of a Public Domain on Shabbos (345:8-10)

Alleyways that are 16 amot wide but not for the entire length.

A dead-end alleyway or an alleyway that is not easily accessed from reshut harabim.

An area in reshut harabim that is between 3 and 9 tefachim high and 4x4 tefachim is a karmelit.