Commentary for Rosh Hashanah 2:4
וּמֵאַיִן הָיוּ מַשִּׂיאִין מַשּׂוּאוֹת, מֵהַר הַמִּשְׁחָה לְסַרְטְבָא, וּמִסַּרְטְבָא לִגְרוֹפִינָא, וּמִגְּרוֹפִינָא לְחַוְרָן, וּמֵחַוְרָן לְבֵית בִּלְתִּין, וּמִבֵּית בִּלְתִּין לֹא זָזוּ מִשָּׁם, אֶלָּא מוֹלִיךְ וּמֵבִיא וּמַעֲלֶה וּמוֹרִיד עַד שֶׁהָיָה רוֹאֶה כָל הַגּוֹלָה לְפָנָיו כִּמְדוּרַת הָאֵשׁ:
And from where did they light the beacons? From the Mount of Olives [facing Jerusalem in the east] to Sarteva, and from Sarteva to Grofina, and from Grofina to Chavran, and from Chavran to Beth Biltin, and from Beth Biltin — they did not leave — but he moved it (the beacon) from side to side and up and down until he saw the entire exile [Bavel] (lit) before him as a bonfire. [For each one would take a torch and bring it up to his roof.]
Bartenura on Mishnah Rosh Hashanah
English Explanation of Mishnah Rosh Hashanah
This mishnah continues to discuss the torches used to let the Jews in the Diaspora know that the new month had been declared in Jerusalem. The mishnah traces a progression from the Mount of Olives in Jerusalem all the way to Babylonia. At Bet Biltin the chain of torches would end for there the one waving the torch in Bet Biltin would be able to see all of the Diaspora lighting their torches in response. The Talmud relates that “Diaspora” here refers to Babylonia.
Since the mishnah is self-explanatory, I will again refrain from commenting.