John had twice earlier reported that the Holy Spirit transported him to another location (in Revelation 4:2 to heaven; in Revelation 17:3 into a wilderness). As in those cases, so now we are not to think that John was physically absent from Patmos. Rather, in some visionary means (it was real, not a dream), John was given unique vantage points so that he could see what the Lord wished to show him.
10 And he carried me away in the Spirit to a great, high mountain, and showed me the holy city Jerusalem coming down out of heaven from God,