DECELEA (Gr. Δεκελεία), an Attic deme, on the pass which led over the east end of Mt. Parnes towards Oropus and Chalcis. From its position it has a commanding view over the Athenian plain. Its eponymous hero, Decelus, was said to have indicated to the Tyndaridae, Castor and Pollux, the place where Theseus had hidden their sister Helen at Aphidnae; and hence there was a traditional friendship between the Deceleans and the Spartans (Herodotus ix. 73). This tradition, together with the advice of Alcibiades, led the Spartans to fortify Decelea as a basis for permanent occupation in Attica during the later years of the Peloponnesian War, from 413–404 B.C. Its position enabled them to harass the Athenians constantly, and to form a centre for fugitive slaves and other deserters. The royal palace of Tatoi has been built on the site.
See Peloponnesian War; also Judeich in Pauly-Wissowa, Realencyclopädie.