876. Houses on the Outskirts of a City

Shabbos 28:2

If there's one house within 70 cubits of a city, a second house within 70 cubits of the first, and a third within 70 cubits of the second - and so on - they are all considered one city even if they extend for a distance that would take days to walk. When the Shabbos boundary is measured, it's measured from the last house that is built for dwelling purposes and that measures four cubits by four cubits (about 6'x6').

Shabbos 28:3

"Dwelling purposes" includes a shul that has a room for the attendant; an idolatrous temple that has a room for its priests; a storeroom, bridge or grave with a living space; a structure four cubits by four cubits that has three walls even if it has no roof; a watchtower; a house on an island; a structure with only two walls that had a roof; a cave with a structure at the entrance that is used as a dwelling. All of these are considered part of the city as long they are fall within 70 cubits and change of it. We act as if a line is drawn along the length of the city from the last structure and we then measure the 2,000 cubits from that line.