Passage: The site of Bat is located inside a palm grove. Around 3000 BC there was an intense trade of copper (extracted locally) and stone (probably diorite) with Sumerians. The necropolis consists of 100 graves and circular buildings each with a diameter of about 20 meters. These buildings have no outside openings, so besides the possibility of their ritualistic function, they may have been used as tanks or silos. Their precise function is as of yet unknown. In 1972, the excavations carried out by a Danish team led by Karen Frifelt showed that the area has been continuously inhabited for 4000 years.

Question: what were the Siberian buildings used for?
tanks or silos