Establishing eruvin for smaller cities and towns - a story of one town (Kankunya) that seeks expertise in calling in someone who knows eruvin. And even so, the expert (Abaye in this case) needs to make sure that the eruv will hold up to the scrutiny of naysayers. I deed, he keeps second-guessing himself. For example, do the homes abutting the river need windows, or really not? Is Mehoza, another city that shifted status from a more public to a more private city, a good parallel, or not really? The process of creating the actual eruv is indeed a challenge! Plus: Abaye then probes whether a given position finds its source in logic or in some tradition -- he is looking for there to be logic. We're seeing the Amoraim work through the cases to the practicality of psak halakhah. Also: A new Mishnah brings us back to techum Shabbat, and determining where the eruv techumin can be set up. Where does the eruv actually need to be placed? Note - Another push for logic.