Nascentes do Alviela

Olhos de Água do Alviela - Spring of River Alviela

Useful Information

Location: Near Amiais de Baxo, follow CM1442 east for 1 km, turn left. Signposted.
(39.446049, -8.709923)
Open: Spring: no restrictions.
Carsoscópio: MAY to SEP Tue-Fri 10-18, Sat, Sun, Hol 11-19.
OCT to APR Tue-Sun 10-18.
Fee: Spring: free.
Carsoscópio: Adults EUR 4.50, Students EUR 2.50, Children (0-5) free, Seniors EUR 2.50, Family (2+*) EUR 10.50.
Groups (10+): Adults EUR 3.50, Students EUR 2, Seniors EUR 2.
Days with free entrance: 16-MAY National Scientist Day, 24-NOV National Day of Scientific Culture, 15-DEC Anniversary of the Alviela Ciência Viva Center
Classification: KarstVauclusian Spring
Light: n/a
Dimension: L=1250 m, VR=215 m.
Guided tours: self guided
Photography: allowed
Accessibility: yes
Address: Centro de Ciência Viva - Carsoscópio, Praia Fluvial dos Olhos de Água do Alviel, Louriceira, 2380-450 Alcanena, Tel: +351-249-881-805.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1880 spring used as drinking water for the city Lisbon.
1961 first diving attempt with 150 m and a depth of 35 m.
04-MAY-1979 protected by Decreto-Lei nº 118/79 as a Natural Park.
1983 J. Michel and J.P. Thiery reach 300 m and 50 m depth.
2004 Franco-Portuguese team reaches 1370 m and 125 m depth.
2008 same team reaches 1510 m and 130 m depth.
2016 AESDA/XploraSub started with the study of of the cave.
2019 special report “Mergulho no Alviela” was presented on SIC national television evening news.
OCT-2020 AESDA/XploraSub reaches 1510 m and 215 m depth.


The nascente do Alviela (source of Alviela river) is a karst spring. It is located at the border between the limestones of Maciço Calcário Estremenho and the sandstones of the tertiary basin Baixo Tejo. It is the resurgence of a 180 km² karstified catchment area. The spring flows all year, but its yield increases after heavy rains. During high yield additional wells are reactivated, for example some springs above the main spring Olhos de Água and the nearby Poço Escuro (Dark Spring). From the spring a picturesque canyon goes uphill, which makes a nice walk during dry times. It may contain a small brook sometimes, but during high yield it is reactivated and filled with a roaring flood.

This is one of the biggest springs in Portugal. During peaks it produces 17,000 l/s or 1.5 Million m³/day. The spring was used for a mill and since 1880 it was used as drinking water for the city of Lisbon. Unfortunately karst is a bad source for drinking water, as the water reappears quite fast and thus pollution from the surface reappears almost unchanged at the spring. For this reason the spring was abandoned some years ago.

The cave was explored by a team of divers in recent years. With a depth of 215 m it is the deepest underwater cave in Portugal, and such depth make it extremely difficult and dangerous for divers to explore. It can only be dived during the dry season, when it is possible to swim through more than 1,250 m of underwater tunnels, with a drop of -215 meters. During the rainy season the strong current and flow rate make diving impossible.

Close to the spring is a museum named Carsoscópio or Centro de Ciência Viva. It has various exhibitions connected with the geology, hydrology, biology and climate of the region. The Geódromo is a virtual reality simulator showing over a period of 175 Million years how this area was formed. The Climatógrafo explains the influence of the climate to the hydrological system of the karst. The Quiroptário, an exhibition on bats and their connection to caves. Caves like the Lapa da Canada are used by the bats as roost.