Bus di Tacoi, Natural cave in Gromo, Italy.

Bus di Tacoi is a cave located on Redondo Mountain at 1500 meters elevation with ascending and descending routes featuring multiple climbing sections. The underground passages and chambers create a complex network that defines the entire structure of this geological formation.

The cave formed over millions of years through limestone erosion that gradually carved out underground passages. This geological process created the network of chambers and routes that visitors explore today.

The name Büs di Tàcoi is Bergamask for "hole of the gracchi", where gracchio means a large mountain crow that nested in the entrance shaft. The cave entrance was long known to hunters and herders before the first explorations.

The cave can only be visited with speleologists who ensure safety during the descent and protect the environment. The entrance lies at 1500 m on a steep gully of Monte Redondo, about an hour's walk along the trail from the Spiazzi di Gromo. A locked gate was installed in 1972 at a depth of 33 m.

One cave route leads to a green lake across complex terrain with significant elevation change. This underground route demands time and stamina but rewards explorers with an unusual destination found within the mountain.