agricultural centre for the surrounding region. Sulphur and potash were mined locally from Minoan times until the 1970s, and were exported worldwide from the nearby harbour of Porto Empedocle (named after the philosopher Empedocles, who lived in ancient Akragas). In 2010, the unemployment rate in Agrigento was 19.2%, almost twice the national average. Main sights 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 Hera 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. The remains of the temple were extensively quarried in the 18th century to build the jetties of Porto Empedocle. Temples dedicated to Hephaestus, Heracles and Asclepius were also constructed in the sacred area, which includes a sanctuary of Demeter and Persephone (formerly known as the Temple of Castor and Pollux); the marks of the fires set by the Carthaginians in 406 BC can still be seen on the sanctuary's stones. Many other Hellenistic and Roman sites can be found in and around the town. These include a pre-Hellenic cave sanctuary near a Temple of Demeter, over which