The Church of Aya Eleni — Hagia Helena — in the centre of Sille is one of the oldest churches in central Anatolia. Tradition holds that it was founded in 327 by Saint Helena, mother of the Emperor Constantine, who is said to have stopped in Sille on her pilgrimage from Constantinople to the Holy Land. The current building is mostly nineteenth-century, but archaeology has confirmed a much older base.
The interior preserves a fine set of nineteenth-century wall paintings — Christ Pantocrator in the dome, scenes from the Gospels and from the lives of Saints — and an iconostasis with surviving icons. The church functioned as a Greek Orthodox parish until the 1924 population exchange, after which it stood empty for decades; restoration in the 2010s reopened it as a museum. Modest dress; the visit takes about thirty minutes.