These 200km labyrinthine caves, 13km from Schwyz in Muotatal, are Europe's longest and the world's fourth-biggest. Think about it – it's 52km from Zürich to Lucerne, so the cave system is about four times as long! You’ll need a guide, sturdy footwear and warm clothing (it's 6°C or 42.8°F in the caves!) to explore them. Trekking Team arranges everything from short tours to overnight bivouac expeditions that include the surreal, 'only-in-Switzerland' experience of a fondue feast in the inky cavern darkness.