The adsorption of subphthalocyanine (SubPc) on the Au(111) surface has been studied by scanning tunnelling microscopy (STM). Depending on coverage and deposition temperature, four different phases have been observed, of which two are coexisting. Spontaneous symmetry breaking inducing mirror domains is observed for all structures. Supramolecular chirality is expressed at different levels and length scale. Our detailed STM study allows conclusions on the origin of polymorphism due to changing coverage and temperature.