Over 200 small and large caves have been found and recorded on the island, of which about half have been designed and researched. Twenty-six of those researched are of great dimensions and apart from the invaluable stalagmites and stalactites, they show signs of human presence during prehistoric and historical times. Some of the most notable ones are: The Cave of Agia Triada (still not fully explored), Arapi (used as a refuge at times of war), Tharounia (found human skeletons from the Neolithic period) , Attali Cave (characterized for sinking a few centimeters every year and the largest cave surface of Evia) and the Caves of Kimi (featuring complex ecosystems which contain information even before human existence).