[Telepathic Intruder]

I wonder how far down I own the land my house is on.

[Scrambler Bob]

I wonder how far down I own the land my house is on. —

And a Chinese is asking the same question.

[ApplegateRanch]

I wonder how far down I own the land my house is on.

That is a very complex question, which depends upon several factors. Generally speaking:

If it's something valuable under there, you own the surface only.

If it's an "environmental hazard" beneath, then you own as deep as it gets.