Oropus or Oropos was a town on the borders of ancient Attica and Boeotia, and the capital of a district, called after it Oropia This district is a maritime plain, through which the Asopus flows into the sea, and extends for 5 miles (8.0 km) along the shore. It is separated from the inland plain of Tanagra by some hills, which are a continuation of the principal chain of the Diacrian mountains.