In the area of ancient Sikyon, town of North East of Peloponesse, the excavations of Greek and American archaeologists led to the finding of the Hellenistic theatre situated at the hill of the acropolis dated back to the end of 4th century B.C. and the early beginnings of 3rd century B.C.. The short distance from the sea combined with the topography of the area cause the saltspray phenomenon, which is strengthened by the direction of prevailing winds in the area. The existence of the above-mentioned salts, caused the phenomena of alveolar corrosion in the structural material. Additionally there is extensive presence of biological depositions, especially penetrating lichens and as a result numerous holes of structural material exist on the surface of monument. Basically, proposed conservation practices are mentioned in the cleaning of depositions and desalination of stone surface and the interior of them with the use of soft chemical products with absorbing clays, neutral detergents and special biocides. The procedure of consolidation will follow, and the protection of surfaces will be effective. The cracking as well as the lost pieces will be completed with the use of traditional mortars.