Kommentar zu Arakhin 9:6
עִיר שֶׁגַּגּוֹתֶיהָ חוֹמָתָהּ, וְשֶׁאֵינָהּ מֻקֶּפֶת חוֹמָה מִימוֹת יְהוֹשֻׁעַ בִּן נוּן, אֵינָהּ כְּבָתֵּי עָרֵי חוֹמָה. וְאֵלּוּ הֵן בָּתֵּי עָרֵי חוֹמָה, שָׁלשׁ חֲצֵרוֹת שֶׁל שְׁנֵי שְׁנֵי בָתִּים, מֻקָּפוֹת חוֹמָה מִימוֹת יְהוֹשֻׁעַ בִּן נוּן, כְּגוֹן קַצְּרָה הַיְשָׁנָה שֶׁל צִפּוֹרִים, וְחַקְרָה שֶׁל גּוּשׁ חָלָב, וְיוֹדְפַת הַיְשָׁנָה, וְגַמְלָא, וּגְדוֹד, וְחָדִיד, וְאוֹנוֹ, וִירוּשָׁלַיִם, וְכֵן כַּיּוֹצֵא בָהֶן:
Eine Stadt, deren Dächer ihre Mauer bilden, oder eine Stadt, die zu Zeiten von Joshua ben Nun nicht von einer Mauer umgeben war, gilt nicht als Häuser in einer ummauerten Stadt. [Ein Haus in einem der folgenden] zählt ein Haus in einer ummauerten Stadt: [die in einer Stadt] mit nicht weniger als drei Innenhöfen mit jeweils zwei Häusern, die in den Tagen von Yehoshua bin Nun von einer Mauer umgeben waren; wie die alte Festung von Tzippori, das Fort von Gush-Halav, altes Yodfat, Gamla, G.'Dod, Hadid, Ono, Jerusalem und andere ähnliche Städte.
Bartenura on Mishnah Arakhin
English Explanation of Mishnah Arakhin
Houses in cities that are not surrounded by walls are not treated in the same way as house in walled cities. These are called houses in courtyards and we will the halakhot which govern them tomorrow. Our mishnah discusses what cities count as being walled.
Bartenura on Mishnah Arakhin
English Explanation of Mishnah Arakhin
If the city does not really have a wall, but its houses are so close together that they look like a wall, it still does not count as a walled city.
Bartenura on Mishnah Arakhin
English Explanation of Mishnah Arakhin
In order for a city to count as a walled city it has to have had a wall around it in the time of Joshua. In other words, the status of walled or not walled is determined by the status of the city when the land was first conquered and then divided up to the original tribes. This is probably because these laws refer to ancestral inheritance, and ancestral inheritance begins at the time of Joshua.
Bartenura on Mishnah Arakhin
English Explanation of Mishnah Arakhin
In order to count as a walled city the city must fulfill two main conditions:
1) Firstly, it must be large enough to be considered a city. The mishnah requires the city to have at least three courtyards, each with two houses.
2) Second, the city has to have been surrounded by walls at the time of Joshua. There are eight such cities listed here. Tzippori and Yodfat are in the Lower Galilee, and Gush-Halav and Gamla are in the Upper Galilee. Gdod (or in other versions, Gdor) is on the other side of the Jordan and Hadid and Ono are in Judea, near Lod. Jerusalem, I am assuming, is familiar to everyone.