PAUL HARCOURT DAVIES / SCIENCE PHOTO LIBRARY PAUL HARCOURT DAVIES / SCIENCE PHOTO LIBRARY
A natural pool in a tufa stream near Castel Fiori, Montegabbione in Umbria. Permanent pools are rare in streams in Umbria, which tend to be seasonal. The depth serves to ensure that in all but the hottest summers there is some water and the ecosystem is thus rich and stable.
Model release not required. Property release not required.