The Temple of Apollo Epicourios (attributed by Pausanias to Iktinos, architect of the Parthenon) stands at an altitude of 1130 meters on Mount Cotilion (W. Peloponnese), founded partly on calcareous rocks and partly on artificial filling. The building material is hard sedimentary limestone of the upper cretaceous. The planes of discontinuity of the stone, and especially the argillaceous veins, contribute to the triggering and evolution of stone deterioration. Thermal fluctuations, very frequent and broad in winter, cause gradual loosening, cracking, and extensive damage to the building material. The effectiveness of some waterproofing materials is tested in accelerated aging laboratory cycles (freeze-thawing). -- AATA