Rabbi Yitzhak bar Yosef quotes Rabbi Yohanan as saying that there is no true reshut ha-rabim in the land of Israel.
Abaye said to Rav Dimi: What is the reason underlying this ruling? If you say this law because Eretz Yisrael is surrounded by the Ladder of Tyre [Sulama d’Tzur] on one side and the slope of Gader [Mahtana d’Gader] on the other side, each formation being over ten handbreadths high and constituting a valid partition, then Babylonia, which is also surrounded by the Euphrates River on one side and the Tigris River on the other side, should not be considered a public domain either. Moreover, the entire world is also surrounded by the ocean, and therefore there should be no public domain anywhere in the world. Rather, perhaps you spoke of the scents and descents of Eretz Yisrael, which are not easy to traverse and hence should not have the status of a public domain?
Abaye asks: “Is Rabbi Yitzhak bar Yosef’s statement because Israel has Sulama d’tzur on one side and Mahtana d’Gader on the other?” That there are natural boundaries on either side of Israel? If so, Babylonia, too has the river Perat on one side and the river Diglat on the other!
The conclusion of the Gemara is that the hills and valleys in Israel create a situation whereby there cannot be a true reshut ha-rabim, which is defined as the area where the twelve tribes grouped in the desert as a people during the exodus. There the ground was flat and easy for even large groups to travel.
The references to natural boundaries in Israel can be identified. Sulam d’Tzur is known today as Rosh HaNikra, where there are high cliffs that stand on the shore of the Mediterranean Sea. The cliffs act as a wall on the western side of the Land of Israel. Mahtana d’Gader refers to the steep drop from the Golan Heights down to the Kinneret along the Jordan River. The vast difference in height and steepness of the drop – the Dead Sea is the lowest spot in the entire world – create the sense of a huge stone wall on the eastern side of the land of Israel.
In the Talmud Yerushalmi, Reish Lakish is quoted as saying that because of the natural boundaries that exist in the world, there really is no reshut ha-rabim anywhere today. Only after the coming of the Messiah, when “every low place will be brought up and every hill and mountain will be lowered” (Isaiah 40:4) will the rules of public domain apply on a biblical level. The question that needs to be asked is why, in fact, do we not rely on these types of natural boundaries for the purpose of eiruvin? On this issue, the reasoning of the Ritva seems compelling. He argues that when boundaries are so far apart that the individual has no sense at all that he is surrounded by them, they cannot really be considered valid for the purpose of eiruvin.