The Stack in Porto di Levante, around 70 metres high, is what remains of a volcanic structure in the north-east part of the Caldera of the Fossa, between here and Vulcanello.
In the second half of 1800, before the eruption of 1888-1890, the Stack was known as “the Factory” because of the intense sulphur and alum mining activity here. Alum was created from the combination of the humid and sulphurous vapours of the water with the clay-like base of the lava that covered the cave. In the Great Stack there are around thirty cavities. From here the Small Stack (Faraglione Piccolo) in front can be admired, a large rocky arch, the remainder of another large cave used for alum extraction. In 1878 the heirs of General Nunziante sold their rights to the Stevensons, who bought the island for £8000 and were already working in the pumice industry in Lipari.