Step into the magic that lies under the ground in Iglesiente, from the red rocks, blue lakes, bright white stalactites and stalagmites to the sparkling transparency of the crystals. The grottoes of su Mannau, in the territory of Fluminimaggiore, are a Karst complex "sculpted" 540 million years ago, and still "living": the calcareous formations are constantly evolving. The cavern winds into the heart of the earth for 8 kilometres, with two main branches: the left originating from the River Placido, with spectacular tunnels and rooms, and the right branch, larger and almost "horizontal", originating from the River Rapido. The visible part is in the first branch, divided into archaeological and speleological parts. The archaeological room is a large hypogeum temple used since pre-Nuraghic times: the remains of oil lanterns found here were part of the rites of a water cult. The cave was connected to the nearby Temple of Antas, which can be reached by a path already traced out by the Romans. The speleological part starts with the Central room, which has to be passed using ropes. Together with the guides, you enter the caves for about 500 metres, in a one-hour excursion that winds through walkways suspended over caverns, waterfalls and pools of clear water, where a tiny, almost transparent and unique species of shrimp (stenasellus nuragicus) lives. Along the left branch, made of large wells and rooms, a ladder leads to the Puddu tunnel. You continue among almost fossilized stalactites as far as the Rodriguez well. From here, a ladder leads up to the panoramic viewpoint. A seven-metre-high column stands in the centre, formed of a stalactite that joined up with a stalagmite to form a pillar. The well is 23 metres deep, and you can climb all the way to the bottom by a ladder. From this point a fossil path leads off, another path linked to the Infinito room, made of alabaster flows, and the Serra room, and a third leads to the River Placido, which flows gently towards the outside. The right branch, on the other hand, has a series of communicating rooms. One after the other you'll see the Sonno room, with 15 metre-high columns, Lake Pensile, 40 metres long and five deep, the Ribaldone room, the highest of all (150 metres), the Bianca room, with its unique stalagmites and aragonites, the Vergine room, the pearl of su Mannau with coralloid and eccentric aragonites, the Bizzarra room, with strange "mushroom" shaped concretions, and the Abeti room, the last known room, 40 metres high with a floor decorated with crystal "fir trees".