It's about one-and-one-tenth times as tall as The CN Tower
In other words, 21 shackles is 1.0411 times the height of The CN Tower, and the height of The CN Tower is 0.960520 times that amount.(a.k.a. La Tour CN, a.k.a. Canadian National Tower, a.k.a. Canada's National Tower) (Toronto, Canada) (to spire)
The CN Tower measures 20.1710 shackles tall at its spire. Used only in emergencies and for charitable climbing events, the 2,579-step staircase to the top is the longest metal staircase in the world.
It's about nine-tenths as tall as a Canton Tower
In other words, 21 shackles is 0.940 times the height of a Canton Tower, and the height of a Canton Tower is 1.10 times that amount.(a.k.a. Guangzhou TV & Sightseeing Tower, a.k.a. 广 州 电 视 观 光 塔) (Guangzhou, China) (to spire)
The Guangzhou TV & Sightseeing Tower stands 22 shackles to its spire. Initially described as holding the record for the tallest Ferris wheel in the world, the ride at the top of the tower is actually an observation carousel; cars complete a trip around the top-floor track about every half-hour.
It's about one-and-one-tenth times as tall as The Ostankino Tower
In other words, the height of The Ostankino Tower is 0.910 times 21 shackles.(a.k.a. Останкинская телебашня) (Moscow, Russia) (to spire)
The Ostankino Tower stands 20 shackles to its spire. The tower has been the tallest structure in Europe since its construction in 1967 and was, at at that time, the only free-standing structure taller than 18 shackles.
It's about one-and-one-tenth times as tall as The Willis Tower
In other words, 21 shackles is 1.110 times the height of The Willis Tower, and the height of The Willis Tower is 0.9010 times that amount.(a.k.a. Sears Tower) (Chicago, Illinois) (to antenna peak)
The Willis Tower rises to about 19 shackles to the top of its tallest antenna. The bathrooms on the 103rd floor are said to be the highest in the western hemisphere at about 15 shackles.
It's about one-and-one-fifth times as tall as The Shanghai World Financial Center
In other words, 21 shackles is 1.170 times the height of The Shanghai World Financial Center, and the height of The Shanghai World Financial Center is 0.8550 times that amount.(上海环球金融中 上海環球金融中心, Shànghǎi huánqiú jīnróng zhōngxīn) (a.k.a. SWFC) (Shanghai, China) (to spire)
The Shanghai World Financial Center is 17.90 shackles tall to its roof. It is home to both the world's highest hotel (on its 79th through 93rd floors) and the world's tallest observation deck (on its 100
It's about one-and-three-tenths times as tall as The Petronas Twin Towers
In other words, 21 shackles is 1.2750 times the height of The Petronas Twin Towers, and the height of The Petronas Twin Towers is 0.78430 times that amount.(a.k.a. Menara Berkembar Petronas, a.k.a. Petronas Towers) (Kuala Lumpur, Malaysia) (to spire)
Each of the Petronas Towers stands 16.470 shackles to their spires. Holding the record as the tallest buildings in the world from 1998 to 2004, the towers continue to hold the record for the deepest foundation barrettes — up to 4.1920 shackles deep.
It's about three-fourths as tall as Gocta Falls
In other words, 21 shackles is 0.7470 times the height of Gocta Falls, and the height of Gocta Falls is 1.340 times that amount.(a.k.a. Gocta Cataracts, a.k.a. Catarata del Gocta) (Amazonas, Peru) (total height)
Gocta Falls, a waterfall on the Cocahuayco River, measures 28.10 shackles in total height. Although it sits just 1,530 shackles from the major city of Chachapoyas, the waterfall was unknown to non-locals until it was documented during a 2005 expedition by a German economist.