Vatnshellir Cave is a cool lava tube on the Snæfellsnes Peninsula in Iceland. It's a popular spot for caving tours, where you can explore the ancient lava formations and learn about Iceland's geology and folklore. The cave is 200 meters long and has some pretty colorful rocks, with reds, yellows, and greens representing different minerals. It's a protected site within the Snæfellsjökull National Park, so you can also check out other nearby attractions like Lóndrangar and Kirkjufell. Just make sure to bring a guide and some sturdy shoes, because it can get dark and slippery down there!