There came to my mind what I shall now speak about, that which will provide us with a basis to begin with. It is that we consider our soul to be like a castle made entirely out of a diamond or of very clear crystal, in which there are many rooms, just as in heaven there are many dwelling places. For in reflecting upon it carefully, Sisters, we realize that the soul of the just person is nothing else but a paradise where the Lord says He finds His delight….
Well if this is true, as it is, there is no reason to tire ourselves in trying to comprehend the beauty of this castle. Since this castle is a creature and the difference, therefore, between it and God is the same as that between the Creator and His creature, His Majesty in saying that the soul is made in His own image makes it almost impossible for us to understand the sublime dignity and beauty of the soul.
Saint Teresa of Avila
The Interior Castle: I:1
Teresa of Avila, St. 1985, The Collected Works of St. Teresa of Avila, translated from the Spanish by Kavanaugh, K; Rodriguez, O, ICS Publications, Washington DC.