'Kyz Kala" means 'Girls' Castle': one story runs that forty girls hid in the Greater Kyz Kala at the time of the Mongol invasion. When they saw what the Mongols had done to the inhabitants of the city of Merv they committed suicide by jumping from the roof. Another local tale identifies the Greater Kyz Kala as the castle for the girls; its smaller neighbour as the boys' castle. It is said that young men wishing 10 marry the girl of their dreams should fire a projectile from the southern castle, to land in the northern one. Given the distance between the two, there are presumably many local bachelors.
The buildings were elite rural residences, and probably date from the 8th or 9th centuries. There remains much debate about the purpose of their distinctive corrugations: theories include helping to keep the interiors cool, ensuring the rapid run-off of potentially destructive rainwater, and simple decoration.
Nobody seems to know for certain why these walls are 'corrugated' in this way. Was it a system of drainage - was it purely decorative? Kyz-kala is one of the most intact ruins in Merv. It's hard to believe that at the height of its fame in the 10-11th century, this pile of ruined brick walls rivaled the great Islamic centers of learning such as Baghdad and Cairo." -in: http://turkmen.traveler.uz/component/content/article/44-turkmen-monuments/210-Kyz-Kala