Koutouki cave is located on the eastern slope of Hymettus, in Peania, at an altitude of 510 m. above sea level. It was discovered in 1928 by residents of the area and was explored and mapped in 1954 by the Greek Speleological Society. The natural beauty of the cave and the fact it is in small distance from Athens contributed to its tourist development in the '60s. For this purpose an artificial entrance in the form of a tunnel was constructed on the west side of the cave and now the tourist route has a length of 350 m.