Around 580-570 B.C., work began on the fourth and largest temple of all, the only one of which remains are visible, and the only one to have been restored. It is an archaic hekatompedon of Ionic style. It is built of local granï-diorite rock, and it has an adyton (for a mystery cult), marble portico (prostasis) with columns forming a monumental entrance, and a marble altar. Ôwï tetrastyle marble colonnades divide the building into three aisles.