It was supposedly the Wine Cellar. Best to go down to shield the valuable old growth vintages.
I was thinking that it would be good to know the elevation of the bottom of the cellar and have a large drain pipe with a shutoff valve to be able to select between high quantity drainage should the water decide to get in from above while having the capability to shut off high surge levels through the bottom; a delicate design exercise.
The house is pretty high up..of course the bunker is going to be much lower..especially if it is a rigged up rich guy SHTF type bunker.
He was bragging before it hit about how well built his place was and that it had hurricane blinds, etc.
I bet a lot of it is leveled.