This paper examines a manifestation of the Jewish perception of space against the backdrop of the Roman conquest, the destruction of the Temple, and the conversion of Jerusalem into the Roman colonia, Aelia Capitolina. I suggest that the rabbinic notion of cities “surrounded by walls,” and their attribution to Joshua, reflects a Jewish reaction to the Roman presence in the land of Israel and the Roman appropriation of the legacy of the cities they subjugated. A consideration of Roman law sheds light on the puzzling attribution of walls to the time of Joshua son of Nun in two rabbinic halakhot: the sale of a house in a walled city and the celebration of Purim and the reading of the scroll of Esther on 15 Adar in walled cities. I suggest that the rabbis introduced the features of a boundary and founding by an ancient figure in order to voice their opposition to the appropriation of Jerusalem by Hadrian and additional Roman emperors, which they marked by founding a pomerium. In addition to the polemical use of the concept of “walled cities from the time of Joshua,” we also find what appears to be application of features of the sanctity of the pomerium to laws of walled cities. This proposed model of polemic, on the one hand, and dialogue, on the other, exemplifies the diverse response by Jews in the land of Israel, and later the province Syria–Palestine, to Roman culture and religion.