abstract: We discuss the class of strongly isometric maps, i.e. maps who preserve the length of every curve, rectifiable or not. It is shown that these maps are prevalent (in the topological sense) in the class of all contractions. on Euclidean space. When considering a similar result on subset of \(R^n\), the openness of the restriction operator with respect to the supremum norm becomes crucial - several positive but also negative results concerning this question are presented.