This section breaks into two parts.
Revelation 21:22–23 relates the fact of the Lord’s own presence in the city (no temple, no light source).
Revelation 21:24–27 records the appeal this city has to the nations, including who and what enters (Revelation 21:25f) as well as who and what may not enter (Revelation 21:27).
22 And I saw no temple in the city, for its temple is the Lord God the Almighty and the Lamb.