The missing room and the tree in our lounge

Underneath our lounge, and between our cave and the boiler room is a mysterious missing space...

It's possible this space is just filled in or was never really there, but (at least in my head) it's equally possible that it contains a chamber of secrets, a treasure room, or anything really (a crypt? a Doctor Who void-space?).

There's no obvious way into this treasure room (we shall call it). The only clear possibility until now has been the large 'water feature' in the middle of our lounge that contains a few plants and a small tree. The estate agent searched fruitlessly for a water connection for some minutes when we looked round the house first (there isn't one), but there is a lot of concrete and lots of bark chip under the plants, potentially hiding something.

So it was with some excitement that we cleared away the bark chips, leaves and old cat poo, and revealed....

...absolutely nothing at all, except a concrete floor. Perhaps there was a trapdoor there which has now been covered.

Anyway, needless to say, this is a great disappointment. There is an old freezer in the basement that backs onto the missing space with an alcove (or door) behind it that we can't quite see.

I shall have to work on moving that to see if we can get to the bottom of our missing room.