mc5 - King AVMA the III

Is it in the human body?

In human body? No. (Unique, remember)

Is it made of stone?

Is it a religious item?

Made of stone? Yes (though that’s perhaps an odd way to put it, given you’ve established that it’s not human-made).
Religious? No.

A cairn?

Cairn? No.

Is it smaller than a double-decker bus?

Is it on Earth?

A geographical feature?

… and the audience awakens …

Smaller than double-decker bus? No.
On Earth? Yes.
Geographical feature? Yes.