It's about half as long as Ha'Penny Bridge
In other words, 21 meters is 0.490 times the length of Ha'Penny Bridge, and the length of Ha'Penny Bridge is 2.04 times that amount.(a.k.a. Droichead na Leathphingine, a.k.a. Liffey Bridge, a.k.a. Droichead na Life, f.k.a. Wellington Bridge) (Quay of Bachelors Walk, Temple Bar Neighborhood, Dublin, Ireland)
The Ha'Penny Bridge, crossing the River Liffey in Dublin, measures 42.9 meters in total length. Over 30,000 pedestrians cross the breach each day.
It's about two-fifths as tall as The Chicago Water Tower
In other words, 21 meters is 0.4480 times the height of The Chicago Water Tower, and the height of The Chicago Water Tower is 2.230 times that amount.(Chicago, Illinois)
The Chicago Water Tower is 46.9 m tall. The tower's architecture was one source of inspiration behind the design of White Castle fast-food restaurants beginning with "Building Number 8," a prefabricated structure built in Minneapolis, Minnesota in 1936.
It's about two-fifths as tall as The Arc de Triomphe
In other words, 21 meters is 0.430 times the height of The Arc de Triomphe, and the height of The Arc de Triomphe is 2.30 times that amount.(Paris, France)
The Arc de Triomphe stands 49 m tall. France's Tomb of the Unknown Soldier from the First World War lies beneath the arch and is commemorated by the first eternal flame to have been lit in modern European history.
It's about two-fifths as tall as Nelson's Column
In other words, 21 meters is 0.40670 times the height of Nelson's Column, and the height of Nelson's Column is 2.4590 times that amount.(London, England, United Kingdom) (from pedestal first step to tip of statue's hat)
Nelson's Column measures 51.64 m from the first step of the pedestal's base to the top of the statue's hat. While the London tower is the tallest, there are at least eight other monuments to Admiral Horatio Nelson, 1st Viscount Nelson, 1st Duke of Bronté throughout England, Scotland, Ireland, Canada, and Barbados.
It's about two-and-a-half times as long as a London bus
In other words, 21 meters is 2.510 times the length of a London bus, and the length of a London bus is 0.3980 times that amount.(Routemaster Double-Decker, RM standard specification)
The Routemaster Double-Decker buses, well-known as icons of London, measure 8.38 m in length. The buses were said to be well-designed for travel in the London traffic, as they offered an open door for riders to board and exit even while the bus was moving at low speeds, and a full-time conductor to collect fares.
It's about two-fifths as tall as The Mahabodhi Temple
In other words, 21 meters is 0.380 times the height of The Mahabodhi Temple, and the height of The Mahabodhi Temple is 2.60 times that amount.(a.k.a. Great Awakening Temple, a.k.a. Maha Bodhi Temple, a.k.a. Temple of Bodh Gaya, a.k.a. Mahabodhi Mahavihar) (Bodh Gaya, Gaya District, Bihar, India)
The tower of the Mahabodhi Temple measures 55 m in total height. The site has been of sacred interest for more than 2,000 years, with the current Temple dating back at least 1,400 years.
It's about two-fifths as tall as The Leaning Tower of Pisa
In other words, 21 meters is 0.3720 times the height of The Leaning Tower of Pisa, and the height of The Leaning Tower of Pisa is 2.690 times that amount.(a.k.a. The Tower of Pisa, a.k.a. Torre pendente di Pisa) (Pisa, Italy) (height along center axis)
The Leaning Tower of Pisa stands 56.4 m tall along the angle of its lean. In May of 2008, in an successful effort to stabilize the tower, 70 tonnes of earth were removed from the tower's base on the side opposite the lean.