Are you referring to Westeros or Essos, perhaps?

If it is the latter, I would recommend "Where the Whores Go" by Ty R.R. Lancaster. He gives a lot of context for what kept "the oldest profession" alive in the east when it seemed to die out in the west. Spoiler alert: centralized religion.

Still waiting on his next book, though.

Written

Documentation of prostitution in Westeros goes back all the way to the crossing of the Arm of Dorne by the First King. One account found in the Citadel of Old Town even suggests that it was a courtesan of the King who first suggested cutting down the Native Weirwoods, because she desired a litter made of the material. The First King was reputed to have brought an entire harem with him in his journey to Westeros. No accounts mention a practice of prostitution by any of the other sentient native species, though some say that the Giants have been known to 'loan out' wives in exchange for favors. Little is known about their culture so this account cannot be verified.

Archaelogical

Research in this area is very limited, given that only three Maesters have ever forged the chain link for Archaeology. Maester Andun, assigned to House Dustin in the North, did take a particular interest in the history of the family and conducted a number of digs in the Great Barrow to learn more about the history of the family. His journal indicates sending a raven to Oldtown consisting of his findings, and indicates that Lord Dustin was not pleased with some of the conclusions drawn about his ancestors. The Citadel never reported receiving the message; it may have been intercepted by Lord Dustin's forces. Some scholars speculate that one of the ancestors of House Dustin was born of a prostitute, and not the Lord's wife.

Additional research in the crypts of Winterfell suggest that there were graves for "companions" near some of the eldest kings. This was often interpreted by the Stark lords to mean traveling companions or simply close friends. But a covert exhumation of one of the bodies by an anonymous party indicated that the bodies were buried with expensive jewels and had a feminine bone structure. The Stark family has denied any further requests to inspect the site.

Sources

• Runes of the First Men, by Daeron Targaryen. Citadel Press, 158 AC.

• Journal of Maester Andun, House Dustin. Citadel Press, 231 AC.

As a follow up and on topic, do we have any idea, written sources/oral traditions/pictographs?, of where whores go?

What is going on in this subreddit today?