The 20-mile Onyx River only exists a few months of the year, but when flowing it is Antarctica’s longest river. Composed of meltwater, the river flows from the Lower Wright Glacier during the few months of Antarctic summer, from late December to late March. Unlike most of Earth’s rivers, Onyx River is unique in that it flows away from the ocean.

Many associate the River Thames with London, but the river covers much more ground than that. The second-longest river in the U.K. (after the River Severn), the Thames begins in the Cotswolds and flows east for 205 miles. Along the way, it passes through the historic university town of Oxford, where it is known as the Isis. The alternate name is derived from the ancient name for the river, “Tamesis.”

The vast Sahara covers 3.6 million miles, making it the largest hot desert on Earth. Although there’s little water throughout the desert, the Sahara is home to two permanent rivers, the Nile and the Niger. The Nile is the longest river in the world, flowing northward through East Africa into the Mediterranean, while the Niger is the principal river of West Africa.

As the word “Avon” is Celtic for “river,” the River Avon literally means “River River.” Located in the United Kingdom and running from the village of Acton Turville in South Gloucestershire down through the spa city of Bath, the scenic river glides by the Cotswold Hills and the Arden woods. The river is associated with the literary works of Shakespeare, who was born and died in Stratford-upon-Avon, a town along the River Avon.

The name “New River” is somewhat ironic considering that — with an estimated age between 260 million to 325 million years old — it's believed to be the oldest in North America. The 320-mile river flows from the Blue Ridge Mountains in North Carolina to West Virginia. Along with the French Broad and the Kanawha rivers, the New River system may very well predate the continent of North America itself.

Set in the middle of the country, Iowa serves as a crossroads of landscapes, cultures, and several major interstate highways. To reach the Hawkeye State from the east or west, though, you must cross a river. Iowa’s entire eastern border is formed by the Mississippi River, while its western border is made up of the Missouri River and the Big Sioux River.

Along the northern part of China's east coast is the Yellow Sea, named for the golden-yellow color of its silt-laden water, which flows in from various rivers. One of those rivers is the Yellow River, China's second-longest river. Running for almost 3,400 miles, the river starts in the Bayan Har Mountains of western China and flows through nine provinces before emptying into the Bohai Sea.

At 26,600 square miles, Lake Victoria is the largest lake in Africa and the world's second-largest freshwater lake. It empties into the White Nile at Jinja, Uganda, which later joins together with the Blue Nile in Sudan to form the Nile River. Formerly known as Ukerewe, the lake was renamed after England’s Queen Victoria by explorer John Hanning Speke in 1858.

From its source high in the Alps of western Italy, the Po heads east for a course of 405 miles, eventually flowing into the Adriatic Sea. The Po marks the boundary between Italy’s Veneto region to the north and the Lombardy and Emilia-Romagna regions to the south. Due to the heavy amount of silt in the Po's waters, the delta area — already the most complex of any European river — is constantly expanding.

If you’ve ever seen crew teams rowing in Cambridge near Harvard University, they’re training on the Charles River. The Charles River runs through the suburbs of Boston before emptying into Boston Harbor at Charlesbank Park. At 80 miles long, the Charles River is the longest river wholly within the state of Massachusetts.

Rising in the Black Forest Mountains of Germany and traveling through nine countries, the Danube collects water from more than 300 tributaries before emptying into the Black Sea. As the second-longest river in Europe, the Danube flows through four national capitals: Belgrade, Serbia; Vienna, Austria; Bratislava, Slovakia; and Budapest, Hungary, all built on the banks of the scenic river.

Although the mighty Mississippi flows 2,348 miles to the Gulf of Mexico and stretches 11 miles across at its widest, it begins as a tiny stream stemming from northern Minnesota’s Lake Itasca. This 1.8-square-mile glacial lake got its fitting name from American geographer Henry Schoolcraft from a combination of two Latin words: “veritas” (truth) and “caput” (head).

The Jordan River feeds the Dead Sea, Earth’s point of lowest elevation on land and the lowest body of water on the planet. So it’s only natural that the Jordan is the planet’s lowest elevation river. The Jordan flows from north to south through Israel and into the Sea of Galilee, sinking to 1,361 feet below sea level at its Dead Sea juncture.

Winding its way through the national capital, the Potomac is aptly nicknamed the “Nation’s River.” The Potomac forms the southern headwaters of Chesapeake Bay, one of the East Coast’s most significant estuaries. Flowing through Virginia and Maryland, the river runs 380 miles to Maryland’s Tidewater at Point Lookout.

Both the Amazon and the Nile outstretch the Yangtze River, but it is the longest river to run entirely through one country, China. The 3,915-mile river is also the longest in Asia, traveling from the Tibetan Tanggula Mountains to the East China Sea. The Chinese name for the river is Chang Jiang, which aptly translates to “long river.”

The Congo doesn’t cross the equator just once; the African river traverses the latitudinal line twice, making it the only major river to do so. The Congo travels approximately 2,920 miles from its water source of the Chambeshi River in Zambia, through the Congo rainforest, and into the Atlantic Ocean. It is the second longest river in Africa after the Nile.

With more than 250,000 rivers, the United States boasts plenty of waterways, but not all are created equal. The country’s five longest rivers are the Missouri (2,341 miles), the Mississippi (2,202 miles), the Yukon (1,979 miles), the Rio Grande (1,759 miles), and the Colorado (1,450 miles). At 1,243 miles, the Columbia River is seventh on the list.

The precise origin of the Amazon River is a matter of some debate. No fewer than five tributaries have been named as the river’s source over the centuries, and all are located in southwestern Peru. The Amazon River flows through five other countries — Bolivia, Brazil, Colombia, Ecuador, and Venezuela — before emptying into the Atlantic.

The River Thames flows for 215 miles and is spanned by over 200 bridges, the most famous of which is the Tower Bridge in London. The name of the river comes from the Latin “Tamesis,” which refers to its dark-colored waters. In 2006, Lewis Pugh became the first person to swim the entirety of the river to raise awareness about climate change.

Flowing for 485 miles, the Seine River is synonymous with Paris and one of Europe’s most historically important rivers. The river begins in the appropriately named commune (municipality) of Source-Seine, France, and runs through the French countryside and Paris before eventually flowing into the English Channel at the French port of Le Havre. It is the second-longest river in France, after the Loire.

The Nile River takes the crown for the world’s longest river, flowing 4,132 miles through 11 countries in northeastern Africa. But this designation is not without dispute — river length can vary according to a variety of factors, and since the Amazon isn’t far behind at 4,000 miles, the Brazilian government has claimed it to be the longest. However, international consensus agrees on the Nile.