The Conhal do Arneiro is an open pit mining where gold was extracted through the gravitational breakdown of the sedimentary deposits on terraces, comprised of conglomerates. The remains of this mining exploitation of Roman origin occupy a region of more than 70 hectares between the Vale stream and the Serra de Sao Miguel. Enormous mounds of pebbles of quartzite which are known as conhos, comprise the excavation heaps. The mounds are aligned in tens of metres, creating the channels where the water circulated for the breakdown of the deposits and washing the sediment. This is the best example of Roman mining exploitation of the "arrugiage" type within the Naturtejo UNESCO Global Geopark and in Portugal. The best points for observation of this geomonument are the Lookout of the Serra de Sao Miguel (Nisa), the Lookout from the Castle (Vila Velha de Ródão), and it is also recommendable to access the Pego das Portas in the Arneiro settlement for a more detailed visit. We suggest a visit to Conhal Interpretative Centre and to the walking trails "Conhal Trails" and "Conhal Gold Mine Trail". In addition to the Roman mining remains it provides for views of the Tejo Valley, the Natural Monument of the Doors of Ródão, griffins and junipers can be observed.