It runs from north to south and flows between the Flecha de Nueva Umbría (Lepe) and Nuevo Portil (Cartaya).

[1] Despite its short length and the small irregularities of the relief, the basin of the Piedras River is quite extensive and has the typical shape of a dendritic drainage, as would be the nerves of a palminervian leaf, especially in its upper basin, where almost 20 streams of the mountain range of Almendro meet in two or three main branches that join in turn, in the Piedras Reservoir as can be seen in the satellite image taken from Google maps (map).

Of all these streams, the most abundant is the one that originates in the municipality of El Almendro, a little more than 1 km to the northwest of Villanueva de los Castillejos.

[6] In order from the source of the river to its mouth, the following mills are registered in the General Catalog of Andalusian Historical Heritage:[7] After passing between the municipalities of Lepe to the west and Cartaya to the east, its mouth in the Atlantic Ocean is parallel to the coast, which is due to a sand tongue or coastal cord, Flecha del Rompido, which runs along a stretch of coastline about 12 kilometers long.

There is a great variety of birds, including endangered species such as the red-crested pochard and the osprey, as well as the little egret and the sandwich tern.