Hello I am glad you have read the book of Psalms 91 when you ask who is the secret place I believe it is a Hidden concealment.
11 He wrapped himself in darkness that covered him like a tent.
He was hidden by dark clouds heavy with water.
He will protect me when I am in danger.
He will hide me in his tent.
He will take me up to his place of safety.
Names of God Bible
20 You hide them in the secret place of your presence
from those who scheme against them.
You keep them in a shelter,
safe from quarrelsome tongues.