Vatnshellir Cave is a lava tube on the Snæfellsnes Peninsula in Iceland, formed 8,000 years ago during an eruption. It's 200 meters long and 35 meters deep, with colorful mineral deposits visible on its walls. Guided tours are available in the summer months, offering a unique caving experience where you can learn about Iceland's geology and folklore. Don't forget to shut off your lights at the deepest point for a taste of total darkness!