Waterfall of la Friera Activity · Illas, Avilés, Asturias Image of Illas, not of the place itself. A waterfall hidden among riverside woodland, reached from La Callezuela by a circular route waymarked as the PR-AS 155, which returns along the path of the valley's mills, several of them still standing. Photo: http://www.facc.info (CC BY-SA 4.0) What to see and do in Illas