A donkey! The shot is taken at Kitheronas mountain. More photos here, here and here.
Canon EOS DIGITAL REBEL XTi, 29/8/2009 7:45, Shutter Speed 1/200, Aperture Value 9.0, ISO 400, EF-S18-55mm f/3.5-5.6 IS, Focal Length 18.0 mm