The natural extension of the ancient Greek Agora, built in the second half of the 1st century BC, with donations from Julius Caesar and Augustus.
The Agora building (111 x 98 m) had a large rectangular atrium surrounded by stoas, shops, and storerooms. The Ionic peristyle that survives dates from the 2nd century AD. The best preserved sections of the colonnades stand on the southern and eastern sides. The west entrance, known as the Gate of Athena Archegetis is in excellent condition.