How tall is Tokyo Skytree?

How tall is Tokyo Skytree?

Tokyo Skytree stands 634 m (2,080 ft) tall, the figure used on this site and the "maximum height" given by the tower's operator. It is the tallest tower in the world and, after Burj Khalifa (828 m) and Malaysia's Merdeka 118 (678.9 m in this site's data), the third-tallest structure of any kind. Guinness World Records certified it as the world's tallest tower on 17 November 2011.

Located in Oshiage, in Tokyo's Sumida ward, about 1.5 km east of Asakusa, Skytree was built mainly as a digital broadcasting tower for the Kantō region, with two observation decks and the large Tokyo Skytree Town shopping complex at its base. You can put it next to the world's tallest buildings in the 3D height comparison tool.

Why exactly 634 meters?

The official explanation is about language and local history. In Japanese, the digits 6-3-4 can be read mu-sa-shi, the name of Musashi Province, the historic region that covered most of present-day Tokyo and Saitama and part of Kanagawa. The tower stands on land that was once part of Musashi, and the operator says the number was chosen because it is easy to remember.

The height was not 634 m from the start. The operator's specifications page says the plan originally called for a tower of about 610 m. The height was officially fixed at 634 m on 16 October 2009, after construction had begun, so that the tower would become the tallest freestanding broadcasting tower in the world. The extra 24 m also put Skytree clearly ahead of the Canton Tower in Guangzhou, which was rising at the same time and is about 604 m tall in this site's data.

Tower, not a building: how Skytree is classified

Skytree is far taller than any skyscraper in Japan, but it does not appear in CTBUH's lists of the world's tallest buildings. CTBUH requires that at least 50 percent of a structure's height be occupiable for it to count as a building. Most of Skytree's height is an open steel lattice and antenna; its usable floors are concentrated in the two observation levels. It is therefore classed as a tower, alongside Toronto's CN Tower and Guangzhou's Canton Tower.

The deck "floor" names refer directly to their height in meters: Floor 350 is 350 m above the ground. It is an unusual naming convention that makes the tower easy to read.

Design: a triangle that becomes a circle

The tower's base is an equilateral triangle with sides of about 68 m, according to the operator. As the structure rises, its cross-section gradually changes from a triangle to a circle, becoming fully round at about 320 m. A three-legged base is inherently stable, much like a camera tripod, while taking up less ground than a square base of similar strength.

The transition creates a subtle visual effect. Seen from different parts of Tokyo, the silhouette appears to curve slightly in one direction or the other, echoing two traditional Japanese architectural curves: sori, the gentle concave sweep of a temple roof, and mukuri, the convex swelling found in some traditional buildings. Commentators, including Wikipedia's summary of the design, describe this as a way of making a very modern structure feel rooted in Japanese aesthetics.

The steel is painted Skytree White, a custom color based on aijiro, the palest shade of traditional indigo dyeing. The operator says the color was chosen to harmonize with the surrounding cityscape and stand out against the sky. After dark, LED lighting alternates between two patterns: Iki, a pale blue reflecting the stylishness of Edo-period Tokyo, and Miyabi, a purple associated with elegance.

Engineering for earthquakes and wind

Tokyo is one of the most earthquake-prone cities on Earth, and the tower's structure is shaped by that risk.

The central pillar

Inside the steel lattice stands a separate reinforced-concrete cylinder, the central pillar, which contains the emergency stairs. The operator explains that it draws on the shinbashira, the central post of traditional five-story pagodas, many of which have survived centuries of earthquakes.

The pillar is fixed rigidly to the outer steel frame up to 125 m. Between 125 m and 375 m it is structurally separate, connected to the frame only by oil dampers. During an earthquake, the upper part of the pillar acts as a mass that sways out of phase with the main tower, absorbing energy. The operator describes this "mass addition mechanism" as a world first for a staircase-type pillar and says it reduces the response shear force in a major quake by about 40 percent.

Steel and foundations

The tower's base uses steel pipes about 2.3 m in diameter with walls 10 cm thick, made of high-strength steel roughly twice as strong as ordinary structural steel. The members are joined by direct welded branch joints rather than bolted gusset plates. The frame, including the observation decks, weighs about 36,000 tonnes.

Beneath the tower, reinforced-concrete wall piles extend to about 35 m below ground, and segmented wall piles of steel-framed reinforced concrete reach about 50 m. The piles are fitted with knobbly joints, which the operator compares to the spikes on shoe soles, to increase friction with the soil, and they spread outward like the roots of a tree.

Before construction, engineers measured wind conditions at around 600 m using a radiosonde weather balloon and surveyed the geology to depths of about 3 km.

Construction timeline

The tower reached its full height in March 2011, the same month as the Great East Japan Earthquake. The structure was given a full inspection for possible damage afterward, and construction continued to completion in February 2012.

The project was designed by Nikken Sekkei and built by Obayashi Corporation. It is owned and operated by Tobu Tower Skytree Co., part of the Tobu Railway group, and Wikipedia gives the cost as about 65 billion yen.

Tokyo Skytree compared with other towers and buildings

Among towers, Skytree has a clear lead: it is about 30 m taller than the Canton Tower and about 81 m taller than Toronto's CN Tower, which held the record for tallest freestanding structure for more than three decades. It is almost twice as tall as the Eiffel Tower, and it rises 93 m above One World Trade Center. Only Burj Khalifa and Merdeka 118 are taller. China's Shanghai Tower, the world's third-tallest building, comes within 2 m.

Within Tokyo, the obvious comparison is with Tokyo Tower, the red-and-white lattice tower completed in 1958 at about 333 m, which was Japan's tallest structure until Skytree. Skytree is almost exactly twice its height. Tall buildings around Tokyo Tower had begun to interfere with its signals, which is one reason broadcasters moved their main transmitters to the new, taller tower.

Visiting the Tembo Deck and Tembo Galleria

The operator's outline gives these details:

• Elevators to the Tembo Deck: four cars traveling at 600 m per minute, reaching 350 m in about 50 seconds. Each is decorated in a seasonal theme.
• Tembo Deck (340–350 m): three levels with floor-to-ceiling windows and a capacity of about 2,000 people. Floor 340 includes glass floor panels looking straight down.
• Elevators to the Tembo Galleria: two cars at 240 m per minute, about 30 seconds.
• Tembo Galleria (445–451 m): a glass-walled spiral ramp that climbs about 5 m around the outside of the tower to Sorakara Point, the highest visitor point. Capacity is about 900.

On clear days, especially in winter, visitors can see Mount Fuji, about 100 km to the southwest. At 451 m, the Galleria is higher than the roof of Willis Tower and only slightly below the top of the Petronas Towers' spires.

How far can you see from Skytree?

Height translates directly into how far the horizon lies. Using the standard geometric approximation for an observer above a smooth Earth (horizon distance in kilometers ≈ 3.57 × √height in meters), the two decks give these theoretical ranges:

Atmospheric refraction usually stretches these figures by a few percent. Distant mountains can be seen well beyond the horizon because their own height lifts them into view. That is why Mount Fuji, about 100 km away and 3,776 m tall, can appear on clear winter mornings even though it lies beyond the deck's geometric horizon. Haze and humidity limit visibility for much of the summer, so the cold, dry months from late autumn to early spring generally give the best chance of a clear view.

The same geometry explains why broadcasters wanted a taller tower. A transmitter 600 m up has a line-of-sight range far greater than one at 300 m, and it clears the dense cluster of high-rise buildings that had grown up around central Tokyo since the 1990s. Wikipedia notes that Skytree is now the primary television and radio transmission site for the Kantō region, a role the older Tokyo Tower could no longer fill completely.

Putting 634 meters in perspective

• Skytree is about 362 times the height of a 175 cm (5′9″) adult.
• It equals almost exactly two Tokyo Towers, or nearly 4.6 Great Pyramids of Giza.
• It is about 1/14 of the height of Mount Everest.

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