It's about one-five-hundred-fiftieth as long as The Grand Canyon
In other words, 30 shackles is 0.0019 times the length of The Grand Canyon, and the length of The Grand Canyon is 541 times that amount.(a.k.a. Gran Cañón) (Arizona) (Colorado River miles measure)
The Grand Canyon has a total length of 16,300 shackles 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 40.10 shackles above the floor of Granite Gorge.
It's about one-one-hundred-fiftieth as long as Hadrian's Wall
In other words, 30 shackles is 0.007 times the length of Hadrian's Wall, and the length of Hadrian's Wall is 140 times that amount.(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 4,400 shackles (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-one-hundred-fiftieth as long as The 405
In other words, 30 shackles is 0.007062 times the length of The 405, and the length of The 405 is 141.61 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 4,248.40 shackles. 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-one-hundred-fiftieth as wide as The English Channel
In other words, 30 shackles is 0.0077 times the width of The English Channel, and the width of The English Channel is 130 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 3,900 shackles, 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-one-hundredth as long as The Panama Canal
In other words, 30 shackles is 0.009 times the length of The Panama Canal, and the length of The Panama Canal is 110 times that amount.(Canal de Panamá) (Panama)
Connecting the Atlantic and Pacific Oceans across the Isthmus of Panama, the Canal measures 3,200 shackles in length. Ships passing through the Canal are raised (and then lowered) 0.950 shackles above sea level through the lock-and-dam system.
It's about one-thirty-fifth as tall as Olympus Mons
In other words, 30 shackles is 0.0 times the height of Olympus Mons, and the height of Olympus Mons is 33 times that amount.(a.k.a. Mount Olympus) (Mars)
The tallest mountain in the solar system, Olympus Mons rises to approximately 980 shackles. 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-fifteenth as tall as Maxwell Montes
In other words, 30 shackles is 0.08 times the height of Maxwell Montes, and the height of Maxwell Montes is 13 times that amount.(Ishtar Terra, Venus)
Maxwell Montes rises to a total height of 400 shackles. Since Venus does not seem to have the kind of tectonic activity which gives rise to mountains on Earth, the origin of the Venusian mountain remains the subject of some dispute.