Perda 'e Liana constitutes one of the most important and evocative morphological conformations in Sardinia. It is a natural monument constituted by a vertical tower, a so-called heel or "tonneri" in Sardinian, that races skywards. At 1293 m, it is one of the best known natural monuments on the island for its strange appearance. It is slender and elegant in form and is two kilometres from the edge of the highland of Tonneri. The highest part of the heel is about fifty metres wide but has vertical walls that rise 100 metres. The light-coloured sides of its walls contrast with the greyness of the rocks that surround it. Its base is in a conical trunk conformation. For the Ogliastra region, this natural monument constitutes the most important evidence of erosion of the large calcareous strata of the Giurese that has covered this part of the island for about ten million years and, being visible over a long distance, constituted a reference point for all those that crossed these mountain zones in times gone by.