The Ploutonion of Hierapolis (Phrygia) is mentioned in numerous Greek and Latin literary sources, which stress its distinctive natural features and the rites that were performed there. From the 19th c. onwards, this sanctuary was the object of investigations and hypotheses on the part of various scholars regarding its exact location, without however reaching a satisfactory solution to the problem. The famous place of worship was finally identified thanks to a large-scale topographic survey of the entire settlement and the surrounding area, undertaken by the Italian Archaeological Mission (hereafter MAIER) as part of the creation of the Atlas (Atlante) of Hierapolis. Specifically, in the area south of the Sanctuary of Apollo, as a result of these investigations various masonry structures belonging to monu-mental buildings were discovered. Also found in the area were sculpted marble capitals with lions attacking bulls and Ionic capitals with masks, which had clearly been brought from the Stoa-basilica, built in the Antonine period along the E side of the North Agora.