The commercial market of Ephesus. Probably founded in 3rd century BC it was extended and got its square shape (154m each side) during the reign of Emperor Augustus (27BC-14AD). It had a central courtyard enclosed on all sides by two-aisled, two-storey halls with business and administrative offices.

You get there going to the left after having passed under the Gate of Mazeus and Mythridates, coming from the Celsus Library.

Some remains are exhibited along the sides, waiting future restoration, I guess.