This has been described variously as both a dragon and a salamander. In any case, it's a gigantic reptile that acts as the park's guardian, emulating the figure of the dragon that, according to Greek mythology, defended the fountains of the Temple of Delphi. (from "Visual Guide, The Project Park Güell") Here is a picture of the full dragon done by Jose Antonio in 2008: http://www.pbase.com/joseantonio/image/134819794

I can't even begin to tell you how difficult it was to capture this famous feature of the park. Everybody wanted their picture taken with it, so it was a matter of waiting for that one second between people posing to get it (poor Jose and my husband!)