From findings in the cavern Harkadio it is proven that the island was inhabited since the Middle-lithic Age. It had a significant flourishing during the 7th B.C. century and the Classical Age. It was conquered as also the rest Dodecanese by the Knights of St. John and the Turks in 1522. It was integrated to Greece in 1948. Tilos is situated between Nissyros and Chalki in an extent of 63 sq.km. and in a distance of 222 n.m. (17 hours) from Piraeus, while you can reach it by speed boat in 55 minutes from Rhodes. The island has magnificent and very clean beaches, imposing mountains, ancient and byzantine monuments, interesting places to explore. Megalo Horio is in a distance of 7 km. from the harbour and is the capital of the island located in the inland in the northern part of the island. It is built amphitheatrically in a hillside, at the top of which ruins of the castle of the Knights of St. John are saved. In the castle there was the acropole of the ancient city and the temple dedicated to Pythian Apollo as well as to the Poliada Athena. 10 km. south-west it is the monastery of St. Panteleimonas, built in a rock side with a green garden. In the Cavern of Harkadio excavations made by the palaeontologists Nicolas Symeonides and George Theodorou brought into light in 1971 instruments and bones from dwarf elephants and deer of the Neolithic Age of the period 8000-7000 B.C. Next to the Cavern Harkadio there is the Small Theater, while over the Cavern it is located the Castle of Missaria, a middle-age building of the Knights of St.John. 7 km. south-east of Megalo Horio it is Livadia, the harbour of the island with very clean sea. Its houses are spread in a fruitful valley and some of them preserve the traditional architectural style. In Livadia dominates the Castle of Agriosykia. In the harbour you can see the church of St.Nicolas and at the seaside the church of St.George.