Placing notes in the Western Wall
Placing notes in the Western Wall refers to the practice of placing slips of paper containing written prayers to God into the cracks of the Western Wall, a Jewish holy site in the Old City of Jerusalem. It is claimed that occurrence of such a phenomenon dates from the early 18th century and stems from the Jewish tradition that the Divine Presence rests upon the Western Wall.
Source: Wikipedia — Placing notes in the Western Wall (CC BY-SA 4.0)