Catechism of the Catholic Church §1795 — excerpt
"Conscience is man's most secret core, and his sanctuary. There he is alone with God whose voice echoes in his depths" (GS 16).
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.