The Knights of the Order of St. John of Jerusalem were a group of elite knights from Europe’s nobility who banded together to defend Jerusalem and the Catholic Church from the Ottoman Empire. They lost Jerusalem, then they lost their next base at Rhodes. They settled on Malta, and in 1565 withstood a siege by the forces of Sultan Suleiman the Magnificent, although quite a few of the knights died.
In 1572 construction on a grand cathedral was begun, now known as St. John's Co-Cathedral in Valletta, Malta. The knights who died in the siege were reburied in the cathedral, and magnificent marble tombstones were inlaid over them, forming the floor of the cathedral. Other nobles were buried in the cathedral until sometime in the 19th century. St. John's Co-Cathedral is an elaborate and intricately-decorated Baroque structure, but the marble floor of tombstones is its most popular feature. Read more about the cathedral and see lot of pictures at Amusing Planet. -via the Presurfer
(Image credit: Flickr user Tony Hisgett)