The Haliacmon is the longest river in Greece, running approximately 200 miles through the country. This river formed Lake Kastoria and continues to feed it. The Haliacmon is also known as the Aliakmon or the Aliakmonas River.
The Haliacmon originates in the Pindus Mountains and travels down through Western Macedonia to empty into the Thermaikos Gulf. The longest rivers that flow through Greece both originate outside of the country. These rivers are the Evros and Axios Rivers. Only small portions of both of these rivers actually run through Greece. The Evros originates in Bulgaria while the Axios originates in F.Y.R.O.M., also known as Macedonia.