Charles Ellicott Commentary Revelation 21:10

"And he carried me away in the Spirit to a mountain great and high, and showed me the holy city Jerusalem, coming down out of heaven from God," — Revelation 21:10 (ASV)

And he carried me away in the spirit . . .—Better, He carried me away in spirit onto a mountain, great and high. It is not merely that the height provides a fine vantage point; the symbolism carries us further. The glimpse of God’s coming glories is best gained from the consecrated heights of self-surrender and prayer. On a mountain apart—the mountain of supplication and separation from the world—is the light and glory of God best seen. There are Beulah heights and transfiguration heights from which we may gain glimpses of the city and the glory of the Lord of the city .

The angel carried away the seer to a mountain great and high, and showed him (not “that great city,” but) the holy city Jerusalem descending out of the heaven from (having its origin from) God. The tempter showed our Lord the kingdoms of the world and their glory; the comforting angel shows our Lord’s prophet the city that has the foundations, and its glory—the city that is of God, its builder and maker (Compare to Hebrews 11:10, where the right rendering is not “a city,” but the city which hath the foundations).