Ruins of a Nuraghe tower in Sardinia.  Developed during the Nuragic Age between 1900 and 730 BC over 7,000 (it is believed there were up to 10,000) of these building ruins consisting of center towers surrounded by smaller stone buildings,  still exist in Sardinia today although thousands of years old and built stone upon stone without mortar.  Little is known about their purpose or the culture that built them.