Access to the fórnia basecoming from:

- Alcanena (± 22 km) by N365 to Moitas Vendas. There take N243 to Alcaria*.

- Porto de Mós (± 6,5 km) by N243 to Zambujal de Alcaria*.

*There follow the signs to Fórnea.

GPS: 39.558333, -8.805278

Access to the top of Fórnea, coming from:

- Alcanena (± 21 km) by N365 to Moitas Vendas. Turn left to Fonte street direction Serra de Sto. António / Serro Ventoso. Antes de Chão das Pias encontra um caminho, para acesso a pé, não sinalizado para a Fórnea. Pergunte aos moradores.

- Porto de Mós (± 10 km) by N362 to Serro Ventoso. At the entrance to Serro Ventoso take Moinho street followed to Principal street. After Chão das Pias is a path to go on foot to the top.

GPS: 39.556731, -8.807993

This is one of the most beautiful and impressive existing natural amphitheaters in Portugal and observing its base (PR9) or the top, with access from Chão das Pias.

Fórnia results from the combination of several factors, and one of the most important is related to the erosive action of the stream of Fórnea, who notched his bedside in margo-limestone formations of the Lower Jurassic – base of Middle Jurassic, sculpting this structure with more than 200 m high and 500 m in diameter. For the modeling also contributed processes related to the combined effect of ice and snow, from colder climatic periods than today, and you can observe gravels forming shed deposits and cryoclast deposits. Fórnea has several temporary springs; the best known is Cova da Velha.

This site has an extremely high biostratigraphic interest because of the information contained in the lithological series that emerges from the bed and along the valley flanks. The sequence of sedimentary rocks that can be observed there, with hundreds of meters width, was deposited in a relatively deep marine environment (Jurassic seas precursors to the Atlantic Ocean). Other than the imposing beauty, the site has high scientific interest in particular stratigraphic, palaeontological/biostratigraphic (for example, in what regards the ammonite fauna), lithostratigraphic and sedimentological, as well high geomorphological value. The deposits of crioclasts are also interesting.

Clast - fragments of pre-existing rocks or minerals that make up a sedimentary rock.

Cryoclast - fragment rock resulting from the breaking of existing rocks due to very low temperature.

Jurassic - geological period in which the dinosaurs dominated and the development of vegetation was abundant. It lasted about 54 million years, roughly between 208 to 144 million years ago.

Marl - sedimentary rock that has a carbonate and a clay component in more or less equal parts.

Stratigraphy - study of sedimentary rocks and associated geological event.