This is a large votive offering, the famous “Moscophoros,” made of marble that was found on the acropolis (5 ft. 5 in. [1.65 m.] high). It is from the Archaic Period, about 560 B.C.
It represents a worshiper bringing a calf to be sacrificed to a deity. The garment that the man wears seems to be quite thin, so that the musculature of the body is clearly visible. The details of his head and that of the calf that he carries are very intricate. The inscription on its base indicates that it was offered by Rhombos to Athena Promachos (Athena, the Defender of the City).
For additional information and images, see the Acropolis Museum website.