If you've never been there check Sant Pau's exact location on Google Map and go visit the place. It is just one subway stop away from Sagrada Familia taking the blue line. You can even get to this modernist complex on foot if you walk all the way up along Avinguda Gaudi from Sagrada Familia.
I wonder what that symbol in the center of the image means. I have read that the monumental lettering as well as part of the mosaic and sculptures make reference to the story of the holy cross and the name of the Hospital's benefactor, banker Pau Gil Serra, who donated the land. So I think this could be a G in the picture but I am not quite sure.