Koutouki Cave is the largest known and one of the most beautiful caves of Attica. It is located at an altitude of 510 m on the eastern fringes of the Ymittos massif in Peania, about 35 km from Athens. It was discovered by accident in 1926 and its interior was first explored two years later. Its mapping was done in 1954 by speleologists Ioannis and Anna Petroheilou. Thanks to its rich stone decoration, Koutouki was highlighted as a tourist destination in the early 1960s by the Hellenic Tourism Organization. In 2000, the use of the space was assigned to the Ministry of Culture.
The unique room of the cave, measuring approximately 60 x 60 m, is divided into smaller ones due to the stone curtain that have developed along the fissures (cracks in the rock due to tectonic phenomena) of the parent rock. The rich stone decoration, with the variety of stalactite formations and colors due to the action of oxides, creates an evocative atmosphere. Today the cave is accessed through an artificial tunnel, 17 m long, built for the convenience of visitors, and the tourist route is 350 m long. The original natural entrance is located on the roof of the cave.
In the framework of the Operational Program of Attica 2007-2013, the Service (Ephoreia) of Paleoanthropology – Speleology carried out a project to renovate the cave facilities and preserve the cave collections, whereupon innovative methods were tested to clean the decoration that had gradually deteriorated during the long-term tourist exploitation. The cave is an organized tourist site.