West of the sacred enclosure, directly opposite the temple of Zeus, was the workshop of Pheidias where the great sculptor crafted the gigantic chryselephantine statue of Zeus, listed as one of the Seven Wonders of the ancient world. The building was erected in the second half of the fifth century, when Pheidias, after completing the sculptures for the Athenian Acropolis, went to Olympia to work on the statue of Zeus. Excavation finds and pottery date it precisely to 430-420 BC. Later the workshop became a place of worship containing an altar for sacrifices to various gods, which Pausanias (V, 15, 1) saw in the second century AD. In the fifth century AD, a Christian basilica was erected over its ruins.

The workshop, a rectangular hall oriented east-west with an entrance on the east side, had the same dimensions (32 x18 x 14.50m) as the cella of the temple of Zeus, probably to facilitate the construction of the statue. Built of shell-limestone, it was divided into three naves by two rows of columns. The statue probably stood in the central, wider nave. It had a wooden core which the sculptor revetted with gold, ivory and glass plaques. These were worked in the adjacent south wing of the workshop, which sheltered the craftsmen. A wealth of excavation finds, including clay matrices for the folds of the statue's robe, pieces of ivory and semi-precious stone, bone goldsmith's tools, glass flower petals and a most important small black-painted oinochoe inscribed Pheidio eimi, or 'I belong to Pheidias', all come from this area. The statue was probably transported in pieces and assembled inside the temple of Zeus. It depicted Zeus seated on a gold throne decorated with mythological scenes; the face and undraped parts of the body were of ivory, while the gold robe was adorned with glass flowers and semi-precious stones.

An Early Christian basilica was erected over the foundations of the ancient building between AD 435 and 451. It had a timber roof, three naves and an apsidal sanctuary at the east end. The low marble chancel screen still survives. The walls were of brick and the floor of marble flagstones, which were dismantled by the excavators to allow for investigation of the ancient levels. The entrance was on the south side of the narthex. Christian inscriptions inside the narthex provide information of the paving of the church floor and on various professions of that time. The basilica of Olympia, the earliest known Early Christian church at Eleia, was destroyed by the earthquake of AD 551.

When the monument was first cleared by the French expedition in 1829 it was already believed to have been originally the workshop of Pheidias. This was uncovered and studied by the German School in the second half of the twentieth century. The architectural members have been gathered inside the narthex of the basilica.