In fact this is an ancient example of sex advertisement.
"A peristyle house behind the Hadrian Temple is known as the brothel. It was built as part of a group of buildings, including the Baths of Scholastikia and lavatories, during the time of Trajan (98-117 AD.). Its function was established with the discovery of an inscription in the lavatories. Entering from the Marble Road, a street sign in the form of a foot engraved on stone indicates its existance. A second entrance gives access from the Street of Curettes. The group of buildings of which it is a part underwent restoration in the 4th century A.D. It is a two-storeyed building, with a large hall on the ground floor,surmounted by a number of small rooms on the floor above, although these are now ruined. (...)"
Is the "original" art? It's almost comical with the foot and woman but I'm sure it probably holds some special deep meaning here. Love the tiny green seedling emerging from that little hole!