A final piece of aggadah before going back to the halakhic details of eruvin: the idea that the Torah is not in the heavens - it's right here for the taking, or, alternatively, it's not going to be accessible for one who is too haughty and refuses to approach Torah with humility. Moreover, don't rely on merchants and traders who may not have the time to study sufficiently. Back to halakhah: how do we determine the boundaries of a city. Filling in bumps and crevices to make smooth shapes for the city from which techum will be measured. We're always increasing the space, with an eye to being lenient for eruv. Also, different types of structures on the outskirts of a town - do they count as houses or not? The question boils down to what is used for residence. Plus: Those who live in huts... (yoshvei tzerifin) - their lives are not lives. The insulting statements here seems to be a comment on the morality of this population - given that the men travel, and maybe the wives were loose or subject to attack in the husbands' absence. And lastly: Torah scholars may not live in cities that don't have vegetables - if you've seen a radish, you've seen the elixir of life.