It's about 0.00000003 times as long as The Rhine
In other words, 3 centimeters is 0.00000002270 times the length of The Rhine, and the length of The Rhine is 44,100,000 times that amount.(a.k.a. Rhein, a.k.a. Rijn, a.k.a. Rhin, a.k.a. Rain, a.k.a. Reno, a.k.a. Rhenus, a.k.a. Ryn) (from near Reichenau, Switzerland through Hoek van Holland, Rotterdam, Netherlands)
The Rhine river runs 132,000,000 centimeters in total length. The World War II Battle of Arnhem, as memorialized in the 1974 book and 1977 movie A Bridge Too Far, was the first of several attempts to capture key bridges across the Rhine, beginning with the Arnhem Bridge in the Netherlands.
It's about 0.00000002 times as long as The Colorado River
In other words, 3 centimeters is 0.00000001290 times the length of The Colorado River, and the length of The Colorado River is 77,500,000 times that amount.(a.k.a. Aha Kwahwat, a.k.a. Grand River, a.k.a. Tizon River, a.k.a. Tecon River, a.k.a. Tison River) (from Grand Lake, Colorado through the Gulf of California)
The Colorado River runs 233,000,000 centimeters in length. Along this length, the river descends from its source, approximately 275,000 centimeters above sea level in the Rocky Mountains, to its mouth in the Gulf of California.
It's about 0.00000001 times as long as The Danube
In other words, 3 centimeters is 0.00000001050 times the length of The Danube, and the length of The Danube is 95,200,000 times that amount.(a.k.a. Donau, a.k.a. Dunaj, a.k.a. Dunav, a.k.a. Duna, a.k.a. Дунав (Dunav), a.k.a. Dunărea, a.k.a. Дунáй (Dunay), a.k.a. Tuna) (from Breg Martinskapelle, Black Forest, Germany through the Danube Delta, Romania)
The Danube river runs 285,000,000 centimeters in total length. Intersecting Vienna, Austria; Bratislava, Slovakia; Budapest, Hungary; and Belgrade, Serbia, the Danube touches more capital cities than any other river.
It's about 0.000000009 times as long as The Oregon Trail
In other words, 3 centimeters is 0.00000000860 times the length of The Oregon Trail, and the length of The Oregon Trail is 116,000,000 times that amount.(from Independence, Missouri to Oregon City, Oregon)
The historic Oregon Trail stretched 349,000,000 centimeters across five (sometimes six) states in the western United States. In the early years of the Trail's existence, the trip was estimated to have taken an average of 160 days.
It's about 0.000000009 times as long as The Volga
In other words, 3 centimeters is 0.00000000850 times the length of The Volga, and the length of The Volga is 118,000,000 times that amount.(a.k.a. Волга, a.k.a. İdel (Идел), a.k.a. Атăл (Atăl), a.k.a. Edil, a.k.a. İdil, a.k.a. Рав (Rav)) (from the Valdai Hills, Tver Oblast, Russia through the Caspian Sea)
The largest river in Europe, the Volga river runs 353,000,000 centimeters in total length. World War II's Battle of Stalingrad between the Nazi Germany and the Soviet Union, which resulted in nearly two million casualties, was fought in part for control of the river.
It's about 0.000000008 times as long as The Mississippi River
In other words, 3 centimeters is 0.0000000079660 times the length of The Mississippi River, and the length of The Mississippi River is 125,500,000 times that amount.(from Lake Itasca, Minnesota through Pilottown, Plaquemines Parish, Louisiana)
The total length of the Mississippi River is 376,600,000 centimeters. Prior to the development of soil erosion programs, the Mississippi River would carry approximately 400 million metric tons of sediment from its banks to the Gulf of Mexico every year.
It's about 0.000000007 times as long as The Distance from L.A. to New York
In other words, 3 centimeters is 0.000000006680 times the length of The Distance from L.A. to New York, and the length of The Distance from L.A. to New York is 150,000,000 times that amount.(Los Angeles, California to New York City, New York) (via I-10 E, I-15 N, I-70 E, I-76 E, I-80 E, I-280 E)
The total length of the freeway route from Los Angeles, California to New York City, New York via Interstate 80 is 449,000,000 centimeters long. This route intersects eleven states and several major cities, including Las Vegas, Nevada; Denver, Colorado; Lincoln, Nebraska; Omaha, Nebraska; Des Moines, Iowa; South Bend, Indiana; and Cleveland, Ohio.