noun
inner sanctuary of a temple; secret knowledge
Literary or formal term. Literally the innermost part of a temple, but often used figuratively for profound, esoteric knowledge or the heart of a teaching.
その僧は堂奥にこもって修行を続けた。
The monk secluded himself in the inner sanctuary and continued his training.
彼の講義は学問の堂奥に触れるものだった。
His lecture touched upon the secret depths of scholarship.