The intriguing formations of Mallos de Riglos are created by compounded layers of gravel.

Red rock formations called Mallos de Riglos near Aguero above the Gallego River in the region of Huesca, Aragon, Spain, Europe. A rock climbers paradise set in the Pre Pyrenean region of Spain is the Mallos de Riglos. The Los Mallos area is also a popular bird watching region where visitors can observe voltures circling in the thermal currents weaving around the rock faces.