Nuraghes are ancient stone-built structures found in modern-day Sardinia. They are generally considered to be the best-preserved and largest Bronze Age remains in Europe.

It's estimated that they were built between 1900 and 730 B.C.. The remains of more than 7,000 of them have now been found. (map here)

There is no consensus on the function of the nuraghes: they could have been rulers' residences, military strongholds, meeting halls, religious temples, ordinary dwellings or a combination of any of these things. Some of the nuraghes are, however, located in strategic places – such as hills – from which important passages could be easily controlled. They might have been something between a "status symbol" and a "passive defence" building, meant to be a deterrent for possible enemies.
Source : Wikipedia