that flow underground from the site of the Terme di Saturnia Spa…
Just upstream from here, the Terme di Saturnia is as luxurious a spa resort as you could hope for, but the 37°C waters that feed it recognise no owner and the naturally carved limestone pools here at the Mill are free to use – 24/7, 365 days a year – for anyone who can find them. They are not as clearly signposted as the spa resort, but they are still, unsurprisingly, one of the most popular natural attractions in Tuscany.