Access to Amiais de Baixo, from:

- Alcanena (± 6 km) – M1442. Before Amiais de Baixo cut to “Olhos de Água”;

- Porto de Mós (± 30 km) – take the road Serro Ventoso, following then to Amiais de Baixo;

- Rio Maior (± 30 km) – N361 to Alcanede / Amiais de Baixo.

At Amiais de Baixo take M1442 following the signs to Olhos de Água or Centro Ciência Viva do Alviela.

GPS:  39.445373, -8.711819

This spring, in the transition area between the Portuguese Estremadura Limestone Massif and the Tertiary Tagus Basin, has the highest flow rate in the country and is an example of the interception of groundwater with surface drainage. The water circulates through a complex system of karstic cavities emerging at the surface through galleries known up to 130 meters deep (surelly they are deeper).

The small relief where is the source is crossed by the Amiais river, whose waters are lost in a cave. After an underground route with about 250 m they come to the surface and run in a narrow valley with vertical walls until they join the Spring waters.

At the base of the escarpment located on the right bank of the Amiais river is small dam fed by the spring and that serves the water catchment for public distribution. Above this is the entrance of the cave of the same name and gives access to the Alviela collector, which is fed mainly by the rainwater that rushes over the plateau of Santo António.

The Alviela River is fed year-round by a permanent spring, but during periods of higher precipitation, water is also discharged through temporary springs, namely by a temporary outflow from the main source (Olhos de Água) and by another located next to the Poço Escuro (dark well). The source of the Olhos de Água of Alviela is one of the most important in Portugal, reaching 17 thousand liters per second and a maximum of 1.5 million m³ of water per day.

From 1880 until recently, the Alviela spring was one of the main sources of water supply to the city of Lisbon (through EPAL), and still "opens doors" to one of the largest fresh water reservoirs in the country.