This classic book is a treatise on the topology of curves. The class of curves considered is quite broad, including smooth curves, rational curves, trees, Cantor curves and so on. It was one of a small handful of landmark books on topology, in particular point-set topology, that were published during the important period of the 1930s. Many of the properties of curves explored by Menger are of renewed importance today in various contexts, notably the topology of dynamics.