Agrigento was founded on a plateau overlooking the sea, with two nearby rivers, the Hypsas and the Akragas, and a ridge to the north offering a degree of natural fortification. Its establishment took place around 582-580 BC and is attributed to Greek colonists from Gela, who named it Akragas. Akragas grew rapidly, becoming one of the richest and most famous of the Greek colonies of Magna Graecia. It came to prominence under the 6th-century tyrants Phalaris and Theron, and became a democracy after the overthrow of Theron’s son Thrasydaeus. At this point the city could have been as large as 100,000 – 200,000 people. Although the city remained neutral in the conflict between Athens and Syracuse, its democracy was overthrown when the city was sacked by the Carthaginians in 406 BC. Akragas never fully recovered its former status, though it revived to some extent under Timoleon in the latter part of the 4th century.

The city was disputed between the Romans and the Carthaginians during the First Punic War. The Romans laid siege to the city in 262 BC and captured it after defeating a Carthaginian relief force in 261 BC and sold the population into slavery. Although the Carthaginians recaptured the city in 255 BC the final peace settlement gave Punic Sicily and with it Akragas to Rome. It suffered badly during the Second Punic War (218-201 BC) when both Rome and Carthage fought to control it. The Romans eventually captured Akragas in 210 BC and renamed it Agrigentum, although it remained a largely Greek-speaking community for centuries thereafter. It became prosperous again under Roman rule and its inhabitants received full Roman citizenship following the death of Julius Caesar in 44 BC.

Ancient Akragas covers a huge area — much of which is still unexcavated today — but is exemplified by the famous Valle dei Templi (“Valley of the Temples”, a misnomer, as it is a ridge, rather than a valley). This comprises a large sacred area on the south side of the ancient city where seven monumental Greek temples in the Doric style were constructed during the 6th and 5th centuries BC. Now excavated and partially restored, they constitute some of the largest and best-preserved ancient Greek buildings outside of Greece itself. They are listed as a World Heritage Site.

The best-preserved of the temples are two very similar buildings traditionally attributed to the goddesses Juno Lacinia and Concordia (though archaeologists believe this attribution to be incorrect). The latter temple is remarkably intact, due to its having been converted into a Christian church in 597 AD. Both were constructed to a peripteral hexastyle design. The area around the Temple of Concordia was later re-used by early Christians as a catacomb, with tombs hewn out of the rocky cliffs and outcrops.
The other temples are much more fragmentary, having been toppled by earthquakes long ago and quarried for their stones. The largest by far is the Temple of Olympian Zeus, built to commemorate the Battle of Himera in 480 BC: it is believed to have been the largest Doric temple ever built. Although it was apparently used, it appears never to have been completed; construction was abandoned after the Carthaginian invasion of 406 BC.