The iconic Nuraghi of Sardinia

Many of the world's great settlements have a distinctive architectural style found in few other places in the world. The Nuraghi of Sardinia definitely fall into this category. Ancient stone structures dotted all over the island, their presence is inescapable, yet understanding of their original purpose has long managed to evade historians. 
 

They may have been used for shelter, as shrines, status symbols, storage, or most likely, for defence, with many being located on hilly strategic positions.  Whatever the purpose, their historic significance has been recognized by UNESCO world heritage, with Su Nuraxi di Barumini on the south of the island offered special protection as representation of the Nuragic people who constructed it.
 

Nuraghi look a little like beehives, with large domed outers, concealing a central tower, the whole structure held together simply by the weight of the stones and some careful application of soil.
 

Perhaps most interestingly, the entrances to Sardinia's Nuraghis seem to point at the angle of sunrise in the winter solstice, which could be to help maximize light during the shortest days of the year, or possibly even part of a more sacred belief.