A narrow trapdoor that goes unnoticed by Park Güell visitors leads to a wonderful and almost magical basement accessible only to a few. It is a large cistern designed by Antoni Gaudí to collect rainwater and supply what was to be a city-garden, and the surplus of which came out in the form of a waterfall by the famous trencadís salamander, which made the overflow functions. The cistern hides curious details that Gaudí left there, who knows if some kind of secret message. The cistern is like a large grotto located, in part, under the hypostyle hall. It is supported by thick columns that are the continuation in the basement of some of the upper space.
An ingenious filtration system allowed water to be stored in this large reservoir, although it seems that it never came into full operation due to the failure of the project promoted by the Güells.
A thorough inspection of the interior of the cistern allows you to discover some mysterious elements whose meaning - if it really has one - Gaudí took with him to the grave. So, in one of the upper corners of the grotto, you can see a curious carved stone that forms perfectly polished angles. Why did Gaudí put it there? Nobody knows. Some think it has to do with some symbolism related to Freemasonry, which equates the mason's work towards ethical perfection with the work of medieval stonemasons in the process of polishing and shaping a rough stone to fit it into the work of a cathedral. Nevertheless, the theory of Gaudí's supposed membership in Freemasonry conflicts with the ultra-Catholicism that the architect professed. Another stone, with rounded shapes, finishes another of the corners. They also bring to mind some red crosses painted on some of the columns, which some even relate to the Templars. In fact, Gaudí's rich symbolism in his works gives a lot.
