Access to Chão de Pias coming from:

- Alcanena (± 23.7 km) – N361 and follow to 25 de Abril street to Louriceira following to S. José street. At Cortiçal entrance turn right to Principal street, direction Chão de Pias.

- Porto de Mós (± 9,6 km) – N362 to Serro Ventoso. There follow to Pebada street and Nova street in Chão de Pias.

GPS: 39.556490, -8.812610

On the plateau of Sto. António and bounded by the reliefs of S. Bento hills in the west, and the top of Fórnea, in the east, Chão de Pias depression is a karst elongated depression about 2 km long. The bottom is covered with terra rossa (red soil) and is a more fertile area than the skeletal soils covering the border zones. This is evidenced by agricultural activities and cattle grazing developed there.

There are doubts on the origin of this depression, having authors classifying it as an uvala, resulting from dolines junction, while others disagree. PhD Alfredo Fernandes Martins (1916-1982), a geographer and one of the leading experts in the Iberian Peninsula in karst relief, including the Limestone Massif of Estremadura, considered that it was a small polje, originate by a watercourse that drained the northern part of the plateau and ending at Chão das Pias river. Due to movements of the massif, this river would have been pendent, continuing to progress by underground galleries, trying to keep the connection to the water line that was affluent. After that karst processes on the surface and in depth have smooth the depression - evidenced by the name "Chãos" meaning floors. The dissolution of limestone and the runoff continued to contribute to the evolution of this depression.

Depression – landform sunken or depressed below the surrounding area.

Doline (also known as sinkhole) - a closed surface depression draining underground in karst landscape. Dolines are usually "bowl-shaped" and can have only a few or many hundreds of meters in diameter.

Karst - A distinctive topography that indicates dissolution of underlying soluble rocks by surface or ground water in areas of easily soluble rocks. Characterized by caves, underground drainage and sinkholes.

Polje – limestone relief form consisting of an elongated and long depression generally flat bottom. Often it has a very steep slope corresponding to a fault. In rainy periods it often becomes a temporary pond.

Terra rossa – Italian expression meaning “red soil”. The terra rossa soil is heavy and clay-rich (silty-clay to clayey) soil, strongly reddish, developed on limestone or dolomite.