I stoped reading just when they re-enter dragom realm due to it's weakening with su han and little white.(realm where he get ton of pills for dragon place) which have palaces/halls as per true dragon(heavenly dragon) son's name.
Around Chapter 703-705. In 703, the palace first appears and they head to it. 704 is them starting to enter it. 705 is them being in there and exploring it.