The ruins of Hierapolis are located a few kilometres North of Laodicea in the Lycus Valley
(western Turkey). This area is characterised by a large geothermic field that produces
several hot water springs along tectonic structures (fractures and faults). Inside Hierapolis is
the Temple of Apollo, the principal deity of the city. While the foundations of this temple go
back to late Hellenistic times, the present remains of the upper structure are from the 3rd
century AD.