Rabbi Yehoshua ben Levi brings two cases - if one acquired residence outside the city and measured the techum from there and it ended in the middle of a city, one's limit ends there. But if it ended at the end of the city, the entire city is like 4 cubits and one continues counting from the other side of the city. Rav Idi questions Rabbi Yehoshua ben Levy as there is no basis for saying this. Is there really no basis? Rav Yosef explains the law in a city that borders on a ravine. Is this considered a city or not for the purposes of measuring techum? Rav Yosef brings a proof from a ruling of Rebbi  regarding people going in between two particular cities, but the gemara explains the reason in a different way and rejects the proof. If there are two cities - one smalla dn one large, if one is in one at the start of Shabbat but has an eruv in the other, does one get 2,000 cubits from the eruv or from the outskirts of the city? Rabbi Akiva and the rabbis disagree. They all agree in the case of an eruv in a cave that one counts 2,000 cubits from the eruv - but in what circumstances? What if one's eruv was outside and the 2,000 cubits ended in the middle of the cave? Shmuel and Rabbi Elazar disagree regarding acquiring residence in a desolate city. Would there be a distinction between one who acquired residence by being there physically or by putting food there? Are there proofs for Shmuel's approach? What are the laws of eruv chatzerot in a courtyard where there are non-Jews?