Criterion (iii): Hierapolis is an exceptional example of a Greco-Roman thermal installation established on an extraordinary natural site. The therapeutic virtues of the waters were exploited at the various thermal installations, which included immense hot basins and pools for swimming. Hydrotherapy was accompanied by religious practices, which developed in relation to local cults. The Temple of Apollo, which includes several Chtonian divinities, was erected on a geological fault from which noxious vapours escaped. The theatre, which dates from the time of Severus, is decorated with an admirable frieze depicting a ritual procession and a sacrifice to the Ephesian Artemis. The necropolis, which extends over 2 kilometres, affords a vast panorama of the funerary practices of the Greco-Roman era.