Jerusalem will be an eternal holy city, present in the heavenly realm and on the new earth (Revelation 21–22).
The graveyard and ash dump were in the Valley of Ben-Hinnom (see study note on Jeremiah 7:30–34) on the south side of the city, and the Kidron Valley was on the east (2 Kings 23:4–6).
The exact location of the Horse Gate on the eastern wall is unknown.