Eruvin 59a and Eruvin 59b, what to do when two measurements of the Shabbat boundaries conflict, and then a digression Mishnah, back to eruvei hatzerot issues, how to allow carrying in a city that was once an ir shel rabim, a city of the public, and then became private, and vice verse. In terms of entrance ways, and rights of passage, and what counts as an opening.
