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Thrown Stones in Bolsena: the columnar basalt that looks like it was hurled by a volcano
The Pietre Lanciate (Thrown Stones) are a columnar basalt formation just one kilometre from Bolsena. Prisms of volcanic rock with pentagonal or hexagonal bases jut out of the ground like spears driven into the soil. A rare geosite, it is closely related to the Giant's Causeway in Northern Ireland, but far less well known.
How they formed
Around one million years ago, lava flows from the Vulsino Complex cooled on contact with water, fracturing into even geometric columns. The process is called columnar jointing, and occurs at a handful of famous sites around the world.
The legend of stones hurled from the sky
The name comes from a folk explanation: locals believed the volcano had flung the stones out during an eruption. There is also another popular legend about a deity who turned lightning bolts into stones to punish rebellious priests.
How to get there
The site is on Via Cassia in the locality of La Fornacella, with a small roadside car park. The area stretches for hundreds of metres, but vegetation covers almost everything: the maintained, visitable section is about ten metres long, preserved by the Municipality as “Geological Heritage”. There is an information panel and a view of the lake, including both the islands of Martana and Bisentina, which alone makes the stop worthwhile.
