Albert Barnes 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. Gave him a vision of the city; seemed to place him where he could have a clear view of it as it came down from heaven. (See Barnes on Revelation 1:10.)

In a great and high mountain. The elevation, and the unobstructed range of view, gave him an opportunity to behold it in its glory.

And showed me that great city, etc. As it descended from heaven. .