The Sanctuary of Sidi el Yamani in T’Zenin, Morocco, is covered with lots of clay because pilgrims whisper their wrongdoings to the walls, then they put wet clay over the spot to modestly hide their sins.
Catholics tell their sins to a priest in Confession, and those sins are not covered over and are forgiven by Jesus Christ. We have His Word for that.
The Charten of Tassiding, India, is considered so sacred that the mere sight of it cleanses a man of all his sins.
Image from 250 Questions About Confession by Fr.John Noone