For thou hast made of a city a heap. Some refer this to Jerusalem; but I think that there is a change of the number, as is very customary with the prophets; for the Prophet does not speak merely of a single city, but of many cities, which he says will be reduced to heaps. As to the view held by some, that the Romans made Jerusalem a palace, it has nothing to do with the Prophet's meaning, which will be easily enough understood, if we keep in remembrance what has been already stated, that the Prophet does not confine his thoughts to those calamities by which the Lord afflicts many nations, but extends his view to the end of the chastisements. In this manner the Lord determined to tame and subdue the obstinacy of men, whom he would never have brought into subjection to him without having been broken down by various afflictions. A palace of foreigners, [1] that it may not be a city. The Prophet does not merely mean that, when the natives have been driven out, "foreigners" wil1 inhabit the cities which have been taken; for that would not agree with what he immediately adds, "that it may be no longer a city;" but that wandering bands of men who shall be in want of a habitation will there find abundance of room, because there will be no inhabitants left. Since 'rmvn (armOn) denotes a magnificent palace, the Prophet thus says ironically, that highwaymen will dwell as in palaces, on account of the vast extent of the place which shall be deserted.

Footnotes

1 - "Of foreigners, a term with the Jews synonymous to barbarians or enemies; as the Romans confounded hospites with hostes, being to them nearly the same thing." -- Stock

For thou hast made - This is supposed to be uttered by the Jews who should return from Babylon, and therefore refers to what would have been seen by them. In their time it would have occurred that God had made of the city an heap.
Of a city - I suppose the whole scope of the passage requires us to understand this of Babylon. There has been, however, a great variety of interpretation of this passage. Grotius supposed that Samaria was intended. Calvin that the word is used collectively, and that various cities are intended. Piscator that Rome, the seat of antichrist, was intended. Jerome says that the Jews generally understand it of Rome. Aben Ezra and Kimchi, however, understand it to refer to many cities which they say will be destroyed in the times of Gog and Magog. Nearly all these opinions may be seen subjected to an examination, and shown to be unfounded, in Vitringa.
An heap - It is reduced to ruins (see the notes at Isaiah. 13; 14) The ruin of Babylon commenced when it was taken by Cyrus, and the Jews were set at liberty; it was not completed until many centuries after. The form of the Hebrew here is, 'Thou hast placed from a city to a ruin:' that is, thou hast changed it from being a city to a pile of ruins.
Of a defensed city - A city fortified, and made strong against the approach of an enemy. How true this was of Babylon may be seen in the description prefixed to Isaiah. 13.
A palace - This word properly signifies the residence of a prince or monarch Jeremiah 30:18; Amos 1:4, Amos 1:7, Amos 1:10, Amos 1:12. Here it is applied to Babylon on account of its splendor, as if it were a vast palace, the residence of princes.
Of strangers - Foreigners; a term often given to the inhabitants of foreign lands, and especially to the Babylonians (see the note at Isaiah 1:7; compare Ezekiel 28:7; Joel 3:17). It means that this was, by way of eminence, The city of the foreigners; the capital of the whole Pagan world; the city where foreigners congregated and dwelt.
It shall never be built - (See the notes at Isaiah 13:19-22)

A city "The city" - Nineveh, Babylon, Ar, Moab, or any other strong fortress possessed by the enemies of the people of God.
For the first מעיר meir, of a city, the Syriac and Vulgate read העיר hair, the city; the Septuagint and Chaldee read ערים arim, cities, in the plural, transposing the letters. After the second מעיר meir, a MS. adds לגל lagol, for a heap.
A palace of strangers "The palace of the proud ones" - For זרים zarim, strangers, MS. Bodl. and another read זדים zedim, the proud: so likewise the Septuagint; for they render it ασεβων here, and in Isaiah 25:5, as they do in some other places: see Deuteronomy 18:20, Deuteronomy 18:22. Another MS. reads צרים tsarim, adversaries; which also makes a good sense. But זרים zarim, strangers, and זדים zedim, the proud, are often confounded by the great similitude of the letters ד daleth and ר resh. See Malachi 3:15; Malachi 4:1; Psalm 19:14, in the Septuagint; and Psalm 54:5, where the Chaldee reads זדים zedim, compared with Psalm 86:16.

For thou hast made of a (b) city an heap; [of] a fortified city a ruin: a palace (c) of foreigners to be no city; it shall never be built.
(b) Not only of Jerusalem, but also of these other cities which have been your enemies.
(c) That is, a place where all vagabonds may live without danger and as it were at ease as in a palace.

For thou hast made of a city an heap,.... Which is to be understood, not of Samaria, nor of Jerusalem; rather of Babylon; though it is best to interpret it of the city of Rome, as Jerom says the Jews do; though they generally explain it of many cities, which shall be destroyed in the times of Gog and Magog, as Aben Ezra and Kimchi; and so the Targum has it in the plural number; perhaps not only the city of Rome, but all the antichristian states, the cities of the nations, all within the Romish jurisdiction are meant; which shall all fall by the earthquake, sooner or later, and become a heap:
of a defenced city, a ruin; or, "for a fall" (c); the same thing is meant as before: it designs the fall of mystical Babylon or Rome, called the great and mighty city, Revelation 18:2,
a palace of strangers; which Kimchi interprets of Babylon, which, he says, was a palace to the cities of the Gentiles, who are called strangers; and it is said, that that city was originally built for strangers, that dwelt in tents, in Arabia Deserts; but it is best to understand it of Rome, as before, which is the palace of such who are aliens from the commonwealth of Israel, and strangers from the covenants of promise, who have introduced a strange religion, and are the worshippers of strange gods, Daniel 11:38. The Targum renders it,
"the house of the gods of the people in the city of Jerusalem;''
and this will be made
to be no city, it shall never be built; any more, when once it is destroyed, signified by the angels casting a millstone into the sea, which shall never be taken up again, or found more, Revelation 18:21.
(c) "in lapsum".

a city . . . heap--Babylon, type of the seat of Antichrist, to be destroyed in the last days (compare Jeremiah 51:37, with Revelation. 18:1-24, followed, as here, by the song of the saints' thanksgiving in Revelation. 19:1-21). "Heaps" is a graphic picture of Babylon and Nineveh as they now are.
palace--Babylon regarded, on account of its splendor, as a vast palace. But MAURER translates, "a citadel."
of strangers--foreigners, whose capital pre-eminently Babylon was, the metropolis of the pagan world. "Aliens from the commonwealth of Israel, strangers from the covenants of promise" (Isaiah 29:5; Ephesians 2:12; see in contrast, Joel 3:17).
never be built-- (Isaiah 13:19-20, &c.).

A city - Which is put for cities: or of enemies of God and his people. And under the name cities he comprehends their countries and kingdoms. Strangers - The royal cities, in which were the palaces of strangers, of Gentiles. No city - Their cities and palaces have been or shall be utterly and irrecoverably destroyed.