Situated in a small ravine outside of Eressos, Moni Pithiarou - or Pithiarou Monastery - is a working monastery dedicated to the Archangels. It's not known exactly when it was founded, but historical records suggest sometime around the early to mid 1500s. The grounds and buildings have undergone something of a renaissance in recent years, and it's become a fascinating corner of the island, with a large lake, productive olive groves and a fine collection of religious relics. It's a peaceful, contemplative spot and well worth a visit.