Title: Natural processes in the degradation of open-air rock-art sites
Subjects: Rock paintings, Conservation and restoration, Petroglyphs, Prehistoric Art, Plein air painting, Art, prehistoric, Art, portuguese, Art, conservation and restoration, Antiquities, Hällristningar, Hällmålningar, Erosion, Vittring, Konservering (museiteknik), Fornminnesvård
Places: Portugal, Cãoa River Valley