There was quite a massive construction in one part of the mansion when he arrived, the efforts put into it being as massive as they could effectively be while Lian Zhiqiu and Madam Liang constantly appeared on the construction site which was first going strong but then seemingly almost disappeared if looked from the outside.
It was a giant underground facility with multiple cultivation chambers of different sizes.
All chambers and the entire facility had formations that trapped Spiritual Qi inside, and as soon as it would be finished, Wu Long would fill it with the incredibly rich Spiritual Qi from the Secret Realm in abundance.
Though of course only using a small portion of what he had as even an advanced formation was not able to hold more than 2-3% of the quantity he absorbed.