The remarkable scheme of dams and reservoirs in the Elan Valley at the turn of the century attracted a great deal of interest and a number of postcards were produced at the time recording the progress of the work. This example shows water pouring over the wall of Pen-y-gareg dam as work continues on building the central tower. The cantilevered timber structure carried a railway track to deliver building materials to the dam - a rather alarming arrangement with water cascading down close by.