"The Belzer Rebbe, Rebbe Ahazon, zatsal, when visiting the wall would search for a certain protruding stone. He would pray at that spot, explaining that his father, Reb Yissachar Dov, zatzal, had told him that this stone was directly opposite the Kodesh Hakodashim (Holy of Holies)." (page 7: http://ohr.edu/ohrnet/5759/bereishi/noach.pdf)
Which stone is it ? Do you have a picture of it or way to find it ?