The rivers in Greece are relatively small in comparison to those in other countries. They follow the direction of the valleys and discharge into the Greek seas. The rivers are generally shallow and turbulent, none are navigable except for the Evros and Loudia Rivers, where vessels can travel along certain sections.
The longest flowing rivers in Greece are the Evros and the Axios Rivers. However, both originate from adjacent countries outside Greek territory; the Evros in Bulgaria and the Axios in F.Y.R.O.M., while the length of the Greek river section is limited). The longest river that originates in the country is the Aliakmon River, which flows through Western Macedonia and empties into the Thermaikos Gulf.
Important ecosystems and hydro-biotopes have formed along the lengths of many rivers, as well as at their estuaries. Many of these are especially well-known and are protected by international agreements.
During the summer months, cultural events are held by many riverside communities, while the visitor can also take part in water sports in many rivers.