From A Wiki of Ice and Fire
Bayasabhad, also known as the City of Serpents, is a fortified city in Essos, located on the Sand Road between the Bone Mountains and the Great Sand Sea. It is one of the three fortress cities that were once part of the Patrimony of Hyrkoon and was founded by the Patriarchs of Hyrkoon.
The city is known for its warrior maids who wear iron rings in their nipples and rubies in their cheeks, similar to those of Kayakayanaya and Shamyriana. It is said that these cities are defended by women out of the belief that only those who give birth are permitted to take life at will.
Like its sister cities, Bayasabhad is ruled by the Great Fathers. Their daughters learn to ride and climb before they learn to walk and are trained in the arts of bow, spear, knife, and sling from the earliest age. Meanwhile, ninety nine of every hundred boys, the sons of the Great Fathers, are gelded when they reach the age of manhood and live out their lives as eunuchs, serving their cities as scribes, priests, scholars, servants, cooks, farmers, and craftsmen. Only the most promising males, the largest, strongest, and most comely, are permitted to mature, breed, and become Great Fathers in their turn. Maester Naylin in his Rubies and Iron speculates on the circumstances that led to such customs.