It does not seem to be a cellar because of those windows. The cellar should be underground and should not have any windows at all.
It's weird that the article isn't showing any images of the interior of the cellar.
The images only show the cellar's entrance in/on the floor.
There is no cellar
It's just a void under the floor.
It's alleged by the article that CB dug it out - but we've yet to see any credible source for that.