wichita.edu
…Mine of Sulphur, through the Roman Plain exerts itself, in divers places, but chiefly, in a certain Lake of unsearchable profundity, four miles distant from the City Tivoli, as also the most famous of the sixteen swimming Islands thereabouts, which they call the Barchettae (or little Barks.) Out of which, the sulphureous River of Tyber has its origine;…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter3.php