On the front side of the castle of Knights, you’ll come across a huge and 500-year-old plane tree. This is called Hippocrates Plane Tree, because it is said that Hippocrates would teach his students under the same tree. Its perimeter is twelve meters and it makes it the largest plane tree in Europe. Its seeds and cuttings have travelled all over the world and some are planted outside of well-known institutions! The tree offers cool shade during the summer, is protected by a metallic rail and in total adorns the center of Kos!