Dunmore Cave

For centuries the relatively small Dunmore Cave has been fascinating writers, archeologists and explorers, and while it's open to visitors today as a lovely bit of geology, it is possibly most famed as the site of a Viking massacre.

The limestone cave, located in County Kilkenny, has been known to modern archeologists since the mid-1800s when the first serious expedition into the depths of the cave was undertaken, however the site was known for centuries prior. The first mention of the cavern is in a 9th century Irish triad poem where it is mentioned as one of the "darkest places in Ireland." The next mention of the cave is the most sensational, however, where the cave gets named in a 17th century manuscript as the site of a Viking battle that took place in 928 CE that racked up 1,000 casualties.

While pieces of gold and silver have famously been found in the depths of the cave, researchers have also found a number of human remains that give some credence to the tale of a massacre (although certainly not enough to prove 1,000 people were killed there).

Since the 1960s the cave has been open as a show cave for visitors to explore. A small amount of safety infrastructure was installed including a roof over the cave mouth to prevent debris from raining down as people enter. However there has been no talk of what's being done about the souls of the restless nords lingering in the air.