Have you ever been on an underground River?

I have never been to Ireland yet but I would definitely want to visit that country one day. I have been to an underground river here in the Philippines. The St. Paul Subterranean River in Palawan, Philippines is one of the country's original ecotourism destinations even before the eco- term became popular. Deep within the limestone and marble peaks of Mount St. Paul flows the Underground River, one of Palawan's most famous spots. Outside the river's mouth is a beautiful lagoon with crystal clear waters that teem with fish. Running about eight kilometers inland, St Paul's Underground River is easily navigable for at least four kilometers. On board a paddle banca (boat) with outriggers, equipped with carbide or kerosene lamps, one enters a new and mystical environment exploring the pitch dark interior recesses of the cavern. Every turn and bend reveal cool stalagmites and huge stalactites merging at the water's surface and reflecting colors from yellow to reddish brown.

We've just visited the Underground River in Palawan on our honeymoon and I'm telling you, it's breathtaking! The formations inside that cave really got me awestruck. Formations like mushrooms and cucumbers really played on our imaginations. There are also formations like the cathedral which looked like an actual cathedral, and an angel. You should really visit that place.. it's worth it.

I've been to an underground river in Palawan, Philippines but I haven't been to Ireland. I visited the link you gave and it sounds amazing. If I get to visit your country I would try to go there, too. :D