It's about as long as Hadrian's Wall.
(a.k.a. Roman Wall, a.k.a. The Wall, a.k.a. Vallo di Adriano, a.k.a. Vallum Aelium, a.k.a. Severus' Wall) (from North Tyneside, Tyne and Wear, England, United Kingdom to Cumbria, North West England, United Kingdom)
Hadrian's Wall, which crossed England form the North Sea to the Irish Sea during the time of Roman rule, measures 600 furlongs (about 79 Roman miles). Roman soldiers — at one time up to 10,000 of them — only occupied Great Britain for about 246 years after the wall was built, after which time the local Brits began to take residence the wall's garrisons.
It's about one-and-one-tenth times as long as The 405.
In other words, 600 furlongs is 1.0357 times the length of The 405, and the length of The 405 is 0.96553 times that amount.(a.k.a. I-405, Interstate 405, San DIego Freeway) (Southern California)
Running from Irvine to San Fernando, The 405 runs a total of 579.32 furlongs. The 405 is the most heavily-trafficed freeway in the United States, with an average speed as low as 8 kph during rush hours.
It's about one-and-one-tenth times as long as The English Channel.
In other words, 600 furlongs is 1.13 times the length of The English Channel, and the length of The English Channel is 0.885 times that amount.(average width between Isle of Ushant and The Walde Lighthouse) (La Manche, Ärmelkanal, Mor Breizh, Mor Bretannek) (a.k.a. The Channel)
The English Channel measures between 532 furlongs, narrowing as it flows northeast. The world speed record for a Channel crossing by swimmer was set by Australian Trent Grimsey in 2012, with a time of 6 hours, 55 minutes.
It's about one-and-two-fifths times as long as The Panama Canal.
In other words, the length of The Panama Canal is 0.71 times 600 furlongs.(Canal de Panamá) (Panama)
Connecting the Atlantic and Pacific Oceans across the Isthmus of Panama, the Canal measures 440 furlongs in length. Ships passing through the Canal are raised (and then lowered) 0.13 furlongs above sea level through the lock-and-dam system.
It's about one-fourth as long as The Grand Canyon.
In other words, 600 furlongs is 0.271 times the length of The Grand Canyon, and the length of The Grand Canyon is 3.69 times that amount.(a.k.a. Gran Cañón) (Arizona) (Colorado River miles measure)
The Grand Canyon has a total length of 2,220 furlongs along the course of the Colorado River at its bottom. Having opened in early 2007, the Grand Canyon Skywalk allows tourists to stand on a horseshoe-shaped glass walkway 5.47 furlongs above the floor of Granite Gorge.
It's about four-and-a-half times as tall as Olympus Mons.
In other words, the height of Olympus Mons is 0.22 times 600 furlongs.(a.k.a. Mount Olympus) (Mars)
The tallest mountain in the solar system, Olympus Mons rises to approximately 130 furlongs. The mountain has been known to astronomers since the nineteenth century because it is tall enough to rise above Mars' frequent dust storms.
It's about one-tenth as long as The Rhine.
In other words, 600 furlongs is 0.0914 times the length of The Rhine, and the length of The Rhine is 10.9 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 6,560 furlongs 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.