Water basins are traces of extracting clay

Here around Siena there are lots of small water basins, measuring 10
meters in diameter on average. They tend to be near country houses, not
far from secondary roads.

They are used for water storage, but it’s not their original end.
Instead, they are what was left by small activities for the extraction
of clay – Siena is renowned for its “crete”.

The country house where I live is in a place once called “la Fornace”,
so it’s very likely that the basins around it were the last places where
clay was extracted before the kiln ceased to work.