How the Dan-yr-Ogof caves were first discovered - and how there's much more left to find

The Dan-yr-Ogof Showcaves were discovered 100 years ago today by local farmers, in the hills of the Upper Swansea Valley. As James Wright finds, they offer a glimpse much deeper into Wales' geological past.

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'100th birthday' for Welsh caves

The spectacular Dan-yr-Ogof cave system at the top of the Swansea Valley was discovered 100 years ago today.