NEAR SAN ANTONIO – New hidden passages outside of San Antonio run 230 feet underground.

It was carved over millions of years and geologists are still discovering new sections along the cave.

Silence and darkness were the only elements in the cave before people arrived.

Brian Vauter, a geologist, has spent his entire career at the Natural Bridge Caverns.

In his opinion, the cave formed 20 million years ago.

Cracks in the ground allowed water to drip through over a long period of time.

The water became the aquifers, ground water supply, used in nearby communities.

Vauter says the aquifer has risen and fallen several times since the caves were formed.

The last time the water was high could have been tens of thousands of years ago.

Watch the video above for the full report.