I suppose it could be an underground stream, though we are only about five feet above the water table.

For a few moments they were in a huge, underground stream.

The passage was fairly straight and had probably been the bed of an underground stream at some time.

"But it's not more than two, through that underground stream."

So many underground streams running through the estate, you see, with all these hills around.

This, then, was almost certainly not the source of pollution, in which case, he must have been following the wrong underground stream.

Yet there was always an underground stream of the truth.

Near the end of the 90-minute tour, steps lead to an underground stream.

In other places, where there are caves, the small underground streams run together to form a river.

That was the second underground stream which went through our class in the weeks before Christmas break.