Fort of Graça

Lest anyone think that the Pentagon had a monopoly on geometry-themed military bases, Portugal's Fort of Graça has a unique star shape that helped the base defend its country for over a hundred years.

Built between 1763 and 1792, the fort features no less than three distinct layers of defense, each separated by walls and ditches. The striking earthwork outer wall is shaped like a huge star, to create overlapping fields of fire from the fortress's cannon. Inside the outer wall is the thick, inner fortification, shaped like a square with huge, raised diamonds of land at each corner. Smaller buildings were constructed on top of the wide corner pieces. In the center of the fort is the main structure, known as the Governor's House, which rises above the rest of the base.  The walls and buildings are decorated with elaborate stonework designs giving the entire complex a feeling of officious luxury.

As the strategic importance of the fort decreased over the years, the base was demilitarized and left in the hands of Portugal's Ministry of Defense who left the site to moulder. Thankfully the Fort of Graça was recently recognized by both the World Monuments Fund and UNESCO as a site to protect. In the end, the greatest enemy this fort has ever seen might be apathy.