Saw an answer to this question recently which I hadn’t really come across before:
Answer (from Muhammad ibn Adam): “According to the consensus (ijma’) of all the scholars, the piece of land on which rests the blessed body of the Messenger of Allah (Allah bless him and give him peace) is more virtuous than anything and everything which includes the Ka’ba and the thrown (arsh) of Allah Most High.”
http://www.daruliftaa.com/question.asp?txt_QuestionID=q-19353442
Anyone know more?