Large cult statue of Artemis of Ephesus. Also called "The Great Artemis", marble, 292 cm high, excavated in the Prytaneion (at the high ground in Ephesus).

Source: ‘Catalogue du Musée d’Ephèse’ 1989.

From the Wikipedia: A Prytaneion (Ancient Greek: Πρυτανεῖον) was seat of the Prytaneis (executive), and so the seat of government in ancient Greece.