Smells can be a serious concern when planning a city. The Mishna on our daf teaches that three potentially bad smelling operations must be kept at least 50 amot from the city – nevelot (animal remains), a cemetery and a burseki (a factory that cures hides and produces leather goods). Furthermore, the Mishna limits the location of a burseki to the east of a city. Rabbi Akiva allows the burseki to be built on other sides of the city, keeping to the 50 amah limit, with the exception of the west side of the city where it cannot be built.
It appears that the special regulations regarding the burseki stem from the fact that the smell of curing leather is much more noticeable than nevelot or a cemetery. The Tanna Kamma‘s regulation limiting a burseki to the east of the city is explained by Rashi as stemming from the fact that winds from the east are usually milder than those from other directions. Tosafot suggest that the stronger western winds would push the smells away from the city. In his Commentary to the Mishna the Rambam explains that strong eastern winds are unusual in Israel.
The Gemara explains Rabbi Akiva’s position as based on the fact that the burseki cannot be built in the west because the west is the place of the Shekhina – the place where God’s presence resides. This revelation leads to a discussion in the Gemara about the appropriateness of facing west during prayer, and whether we should perceive God as having a physical place and presence or if we should work with the assumption that Shekhina be-khol makom – that God’s presence is everywhere.
Tosafot and others point out that the discussion of God’s place seems to run counter to the commonly held halakha – whose source is in Gemara Berakhot – that the direction for prayer is always towards Jerusalem and the Temple Mount. The Ramah argues that we need to distinguish between our Gemara’s attempt to clarify a point about God’s presence and the ruling that we relate our payers to Him via the place of the Temple.