אורח חיים תרפ״חOrach Chayim 688

Se’if 1א׳

כְּרַכִּים הַמֻּקָּפִים חוֹמָה מִימוֹת יְהוֹשֻׁעַ בִּן נוּן, אֲפִלּוּ אֵינָן מֻקָּפִין עַכְשָׁו, קוֹרִין בְּט"ו, אֲפִלּוּ אִם הֵם בְּחוּצָה לָאָרֶץ, וַאֲפִלּוּ אֵין בָּהֶם עֲשָׂרָה בַּטְלָנִים (פי' בַּטְלָנִים מִמְּלַאכְתָּם וְעוֹסְקִים בְּצָרְכֵי צִבּוּר); וְהוּא שֶׁהֻקַּף וְאַחַר כָּךְ יָשַׁב, אוֹ שֶׁיָּשַׁב תְּחִלָּה עַל דַּעַת לְהַקִּיפוֹ אַחַר כָּךְ, לַאֲפוּקֵי כְּשֶׁנּוֹדַע שֶׁיָּשַׁב תְּחִלָּה עַל דַּעַת שֶׁלֹּא לְהַקִּיפוֹ אֲבָל בִּסְתָמָא הֻקְּפָה וּלְבַסּוֹף יָשְׁבָה (רַ"ן).

The law for cities which were surrounded by a wall in the days of Yehoshua Bin Nun, 8 Seifim: Cities that had a wall surrounding it at the time of Yehoshua Bin Nun, even if they currently do not have a wall surrounding them, read the Megillah on the 15th of Adar, even if they are outside the Land of Israel, and even if they do not have ten Batlanim (explanation: people who are unemployed and who busy themselves with the needs of the congregation). The above refers to [cities that are] surrounded, and afterwards were settled, or were settled at first with the plan to build a wall surrounding them afterwards - this comes to exclude [a city in which] it becomes known that it was settled with the original intent not to surround it [with a wall] [but a plain case scenario can be assumed to [involve a city] surrounded and then settled] [the R"an].

Se’if 2ב׳

וְכֵן הַכְּפָרִים הַנִּרְאִים עִמָּהֶם, אֲפִלּוּ אֵינָם סְמוּכִים, כְּגוֹן שֶׁהֵם בָּהָר; אוֹ שֶׁסְמוּכִים לָהֶם, אֲפִלּוּ אֵינָם נִרְאִים עִמָּהֶם, כְּגוֹן שֶׁהֵם בָּעֵמֶק, וּבִלְבַד שֶׁלֹּא יִהְיוּ רְחוֹקִים יוֹתֵר מִמִּיל. וּבְשׁוּשָׁן אַף עַל פִּי שֶׁאֵינָהּ מֻקֶּפֶת חוֹמָה מִימוֹת יְהוֹשֻׁעַ, קוֹרִין בְּט"ו הוֹאִיל וְנַעֲשָׂה בּוֹ הַנֵּס.

And likewise the villages which are visible with them [the "walled" cities], even though they are not [directly] adjacent to them, such as when they are [together] on a mountain. Or they are adjacent to them even though they are not visible to them, such as when they are in a valley, provided they are not farther than a mil. And in Shushan, even though it was not surrounded by a wall from the days of Joshua, they read on the 15th [of Adar] because this is where the miracle occurred.

Se’if 3ג׳

כְּפָרִים וַעֲיָרוֹת גְּדוֹלוֹת, וּכְרַכִּים שֶׁאֵינָם מֻקָּפִים חוֹמָה מִימוֹת יְהוֹשֻׁעַ בִּן נוּן קוֹרִין בְּי"ד.

Villages, large towns and cities that did not have a wall at the time of Joshua the son of Nun read on the 14th.