For millennia the door has fulfilled an architectural and social function. In cities it represented a key element in its defense, in houses it preserves us from inclement weather and also safeguards our privacy. It is not surprising that in this long coexistence of opening of passage and closing, a symbolic meaning has developed, this has always indicated the passage from one state to another, what is known to the unknown, from ignorance to knowledge or darkness to light. The door not only alludes to a barrier, but also to a certain psychological state that constantly invites us to cross it. In both Christianity and Hermeticism the door indicates the opening that brings us closer to the Holy Santorum of divinity, it is separation from the sacred to the profane (pro-outside fanus-temple). In Christian symbolism Jesus referred to himself as the door behind which was salvation and eternal life, represented by the tympanum with the figure of Jesus; he said, "I am the door, whoever enters through me is safe" (Saint John 10,9). Saint Teresa writes in the "The Mansions", comparing the soul to a castle that must be conquered, "Because as far as I can understand the door to enter this castle is prayer." In Greco-Roman Mythology, the doors of Hades or kingdom of the dead, they were oriented towards the west where the sun sets, where Charon transported the deceased with his boat after having paid for it with a coin that at the time of burial was deposited together with the body; there are references in the Iliad, the Odyssey, or the Aeneid. Late in the Middle Ages the doors were guarded by sculptures representing symbolic animals, such as dragons or other fabulous animals, and even in the Renaissance it was frequent to put the end of a monster, holding between its jaws a ring. Also, in Hermeticism, the door is usually protected by a monster or a guardian armed with a sword to prevent the entrance to the knowledge of aspirants who have not become worthy of it, this door is low threshold that is usually crossed by lowering the head or kneeling. In hermetic science, opening a door always carries a risk because even if we do not cross it or close it again afterwards, the vision of what is behind will never be erased from our mind, we will keep it in mind until our end. Sovena said that the door of happiness opens by stretching, because if we push it, it closes more and more.