The Río Atrato is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 of northwestern Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

. It rises in the slopes of the Western Cordillera

Cordillera Occidental, Colombia

The Cordillera Occidental is one of three branches of the Andes Mountains in Colombia that divide at the Node of Pasto, extending from south to north from Nariño to the Node of Paramillo in Córdoba....

 and flows almost due north to the Gulf of Urabá

Gulf of Urabá

The Gulf of Urabá is a gulf on the northern coast of South America. It is part of the Caribbean Sea. It is a long narrow inlet in the coast of Colombia, close to the connection of the continent to the Isthmus of Panama. The town of Turbo lies at the southern end of the Gulf...

 (or Gulf of Darién

Gulf of Darién

The Gulf of Darién is the southernmost region of the Caribbean Sea, located north and east of the border between Panama and Colombia. Within the gulf is the Gulf of Urabá, a small lip of sea extending southward, between Caribana Point and Cape Tiburón, Colombia, on the southern shores of which is...

), where it forms a large, swamp

Swamp

A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...

y delta

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

.
Its course crosses the department of Chocó

Chocó Department

Chocó is a department of Colombia known for its large Afro-Colombian population. It is in the west of the country, and is the only Colombian department to have coastlines on both the Pacific Ocean and the Atlantic Ocean. It also has all of Colombia's border with Panama. Its capital is...

, forming that department's border with neighbouring Antioquia

Antioquia Department

Antioquia is one of the 32 departments of Colombia, located in the central northwestern part of Colombia with a narrow section that borders the Caribbean Sea. Most of its territory is mountainous with some valleys, much of which is part of the Andes mountain range...

 on two occasions.
Its total length is about 650 km (403.9 mi), and it is navigable as far as Quibdó

Quibdó

Quibdó is the capital city of Chocó Department, in western Colombia. The municipality of Quibdó has an area of 3,337.5 km² and a population of 100,000 mainly consisting of Afro Colombians and Zambo Colombians. Quibdo serves a a receptor for those persons affected by the Colombian armed...

 (400 km / 250 mi).

Flowing through a narrow valley between the Cordillera and coastal range, it has only short tributaries, the principal ones being the Río Truando, the Río Sucio, and the Río Murri. The gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 and platinum

Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

 mines of Chocó line some of its confluents, and the river sands are auriferous.

The Atrato at one time attracted considerable attention as a feasible route for a trans-isthmian
canal, but any such plans were abandoned in favour of the Panama Canal

Panama Canal

The Panama Canal is a ship canal in Panama that joins the Atlantic Ocean and the Pacific Ocean and is a key conduit for international maritime trade. Built from 1904 to 1914, the canal has seen annual traffic rise from about 1,000 ships early on to 14,702 vessels measuring a total of 309.6...

.