Once upon a time, here lay the dam of Vallvidrera’s swamp that supplied drinking water to Sarrià. In the mid 1860’s it was a feat in engineering as it is a reservoir built with billets, 50 meters long, 3 meters wide and 15 meters high. Next to it, the Grott quarry was the one that took the water to its final destination. The quarry later became a 1.5km electric train track for passengers in an effort to create an amusement park called Lake Valley. The inside of the tunnel was lit up by different coloured lights.
The whole site is now a natural park protected to preserve some local fauna and provide hikers and walkers an opportunity to enjoy nature, stretch their legs and end up on the wrong path. Even if you do, there is still enough routes to enjoy in the area.