Tufa is a limestone deposit in streams. Streams fed by springs on limestone grassland (typical in our area) generally contain dissolved calcium bicarbonate as a result of slightly acid rain (as a result of dissolved carbon dioxide) attaching the calcium carbonate of the limestone. However, photosynthetic organisms growing in the water extract carbon dioxide and change the pH causing calcium carbonate to precipitate again. It is there a sign of clean water.  

Articles describing walks or mentioning walking routes.