Didyma was an ancient Ionian sanctuary. It had a temple and oracle of Apollo. Didyma was the most significant sanctuary in the territory of Miletus.
The oldest tablets dated back to the 6th century BC. Most of the sculptures, form the same century, were carried out to British Museum by Sir Charles Newton in 1858, of course with the permission of Ottoman authorities. German excavations made between 1905 and 1930 revealed most part of the temple.
The huge marble temple has amazing, 120 giant columns at the front porch. Because the giant size of the construction, it never covered by a roof.
At the back of the porch, temple priests met petitioners. They accept questions for the oracle, and to deliver oracular poems.
Two tunnel ramps slope down from both sides of the porch to the huge square. This square held the sacred spring. A priest would drink from the spring to produce oracle.
Several impressive sculptures are around the temple, especially the head of Medusa. It is similar to the head of Medusa in the Basilica Cistern in Istanbul.