Grotta di Su Mannau, Natural cave system in Fluminimaggiore, Sardinia, Italy.
Grotta di Su Mannau is a cave system in Fluminimaggiore that stretches for about 8 kilometers underground beneath the limestone. The interior contains crystal-clear lakes, waterfalls, and rock formations shaped by water flow and erosion throughout its long existence.
The cave system formed roughly 540 million years ago through natural karst processes as water dissolved the limestone. Archaeological evidence reveals that people living in pre-Nuragic times used it as a sacred underground space.
The place held spiritual meaning for early Sardinians, who viewed underground waters as sacred and left behind clay oil lamps as evidence of their rituals. Local people today recognize it as part of their island's subterranean heritage.
Visitors can join guided tours lasting about one hour that cover 500 meters of the left branch with elevated walkways. The paths are built above underground water features, making the walk safe and manageable for most people.
The cave waters are home to Stenasellus nuragicus, a type of shrimp found nowhere else in the world. This tiny creature has adapted perfectly to life in complete darkness and the isolated underground environment.
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