One of the things that the volcanic ground of Banyoles has is a few warm springs, so years and years ago, there was a health spa called "la Puda". The water from the fountain is kind of whitish and smells like rotten eggs due the suplhur levels. It's abandoned now and taken over by plants and trees.
It's a very interesting experience walking around the grounds; there's a road in front of the main entrance but it's not all that used so sometimes it felt quite strange the loneliness of the place. Also, I got bitten by what it seemed a whole population of mosquitos (like always, I'm a friggin magnet).