Tokyo Skytree stands 634 metres high, but that was not the number the project started with. Its operator states that the height was initially set at approximately 610 metres, and that 634 was settled on only after the decision to aim for the tallest free-standing broadcasting tower in the world. Guinness World Records certified it as the world’s tallest tower on 17 November 2011, and it was completed in 2012. The address is 1-1-2 Oshiage, Sumida-ku, postcode 131-0045.
634 was chosen because the digits read as the name of an old province
The operator gives the reason for the exact figure, and it is not structural. Wanting a height that was straightforward to remember, the project settled on 634 because the three digits sound out as Musashi, the name of one of the old provinces. The operator describes Musashi Province as a large area taking in parts of Tokyo, Saitama and Kanagawa, states that historical records place the tower’s site inside it, and adds that the province can be seen from the observation decks.
The tower nearly doubled the tallest structure Japan had, and the same firm designed both
When the construction site was fixed as the Oshiage district of Sumida Ward in 2006, the tallest structure in Japan was Tokyo Tower, completed in 1958 at approximately 333 metres. The operator describes the new tower as an attempt, approximately 50 years later, at nearly double that height, and calls it a challenge into uncharted territory.
The operator’s own page on structural design names the designer of Tokyo Tower in passing, and it is Nikken Sekkei. The same firm is listed as the design and supervision office for Tokyo Skytree. Dividing 634 by 333 gives 1.90, so the later tower is a little under twice the earlier one, by our division.
The wind at 600 metres and the ground 3 kilometres down were both surveyed before design
Because no structure in Japan had reached that height, the operator states that the work began with research rather than drawing. To find out what winds blow 600 metres above the ground, a weather balloon called a radiosonde was launched to measure the distribution of wind speed and the turbulence at high altitude. On the ground, alongside ordinary surveys, a microtremor array survey was used to investigate the deep geological structure down to about 3 kilometres, so that the shaking of this particular site in an earthquake could be simulated more accurately.
The foundation was then designed to be pulled on as well as pushed down. The piles are made wall-like with knuckles along them to raise frictional resistance, which the operator compares to the soles of spiked shoes, and they are connected and spread radially underground. The above-ground steel frame is continuously joined to those piles so that force passes straight into them.
The base is a triangle, and the first column weighed 29 tons on its own
The foot of the tower is triangular, with each side approximately 68 metres long; the operator’s note on this is that three is the smallest number of points that gives stability. The steel framework of the tower, including the observation decks, weighs approximately 36,000 tons.
The first above-ground steel column was photographed on 6 April 2009. The operator gives its dimensions as approximately 4 metres high, 2.3 metres in diameter and 10 centimetres thick, weighing approximately 29 tons. The structural members are high-strength steel pipes of about twice the strength of standard steel, and the pipes at the base of the tower measure 2.3 metres across with a 10-centimetre wall. The frame is a truss of main, horizontal and diagonal members joined in triangles, welded to each other directly by a method the operator calls branch joints, without connecting plates.
The central shaft is a counterweight, and the idea came from a five-storey pagoda
The vibration-control system is the part the operator explains at greatest length. A reinforced concrete cylinder at the centre of the tower, with an emergency staircase inside it, is structurally separated from the steel-framed tower around it, and the upper part of that cylinder is left to act as a weight.
The principle is described as a mass addition mechanism: an added weight is made to vibrate out of step with the building, so that the two cancel each other, and the operator puts the reduction in response shear force during a major earthquake at about 40 per cent. Steel or concrete blocks are the usual added mass, and the operator notes that large equipment and heat storage tanks have also been used, but states that this is the world’s first case of using a central shaft containing a staircase as the added mass.
The name given to the system refers to the central pillar of a traditional pagoda. The operator’s claim about pagodas is carefully bounded: a five-storey pagoda is a wooden form found only in Japan, there have been cases of collapse from typhoons and from fire, and there are no records of one collapsing because of an earthquake. It adds that the reasons for that resistance are disputed and that the central pillar is believed to play a large part.
There are two observation levels, and the higher one is a slope
The lower level is the Tembo Deck at floor 350, with restaurants, a cafe and shops on it. The upper level starts at floor 445 and climbs: the Tembo Galleria is a sloping walk that arrives at floor 450, where the highest point of the publicly accessible structure sits. The operator gives the capacity of the Tembo Deck as approximately 2,000 people and that of the Tembo Galleria as approximately 900.
Above both of them, at the 634-metre top, is the digital broadcasting antenna.
The lift to the first deck runs two and a half times the speed of the one above it
Four lifts run from ground level to the Tembo Deck at 600 metres per minute, taking approximately 50 seconds. Two more run from the Tembo Deck to the Tembo Galleria at 240 metres per minute, taking approximately 30 seconds. The lower set therefore travels 2.5 times as fast as the upper set, by our division, over roughly 20 seconds more of travel time.
| Item | Figure the operator publishes |
|---|---|
| Tower height | 634 m |
| Length of one side of the foot | Approximately 68 m |
| Weight of tower steel framework including decks | Approximately 36,000 tons |
| Tembo Deck capacity | Approximately 2,000 people |
| Tembo Galleria capacity | Approximately 900 people |
| Lifts, ground to Tembo Deck | 4 units, 600 m per minute, approximately 50 seconds |
| Lifts, Tembo Deck to Tembo Galleria | 2 units, 240 m per minute, approximately 30 seconds |
| Operating company | TOBU TOWER SKYTREE Co., Ltd. |
| Design and supervision | Nikken Sekkei Ltd. |
| Construction | Obayashi Corporation |
The tower exists to transmit television, and the reason is other buildings
The operator states the main role plainly: transmitting terrestrial digital broadcasting. Terrestrial digital broadcasting began in the Kanto region in December 2003, and the problem it ran into was the city centre itself, where the operator counts numerous 200-metre-class skyscrapers with the potential to affect the transmission of radio waves. Moving to a 600-metre-class tower roughly doubles the transmission height for terrestrial digital broadcasting, which is how the operator describes the fix. It also expected the coverage area to widen for One-Seg, the digital service for mobile devices that began in April 2006, and describes the tower as serving as a disaster-prevention tower in an emergency.
Nine years and five months separate the first proposal from the six companies going on air
The operator’s history of the project runs from a December 2003 launch of a new-tower project by six Tokyo-based television companies, through a request to Tobu Railway in December 2004 and that company’s announcement of intent in February 2005, to the final selection of the Sumida and Taito area as the site in March 2006. Reservation agreements with the six television companies were signed in December 2007, the name Tokyo Skytree was decided in June 2008, construction began in July 2008, and TOKYO MX signed in December 2008.
Transmission then arrived in stages rather than all at once. FM radio for NHK and J-WAVE and a taxi radio system began in April 2012. TOKYO MX started simulcasting from both Tokyo Tower and Tokyo Skytree in October 2012 and completed its move in May 2013, the same month that six television companies began broadcasting: NHK, Nippon Television, TV Asahi, TBS Television, TV Tokyo and Fuji Television. FM complementary broadcasting for three Tokyo AM radio stations, TBS Radio, Nippon Cultural Broadcasting and Nippon Broadcasting System, began in December 2015. From the December 2003 launch of the project to the six companies going on air in May 2013 is nine years and five months, by our subtraction.
Four national research bodies use the tower as an instrument
Alongside the observation decks and the broadcasting equipment, the operator lists the tower as a research site and names the four organisations using it: the Central Research Institute of Electric Power Industry, the National Institute for Environmental Studies, the National Research Institute for Earth Science and Disaster Resilience, and the National Institute of Advanced Industrial Science and Technology.
Admission to the decks is priced separately from all of this, and the price has been set day by day since April 2026.
Sources Checked
Tokyo Skytree — official page on specifications
Confirmed that the maximum height is 634 metres; that the height was initially set at approximately 610 metres and changed after the decision to aim for the world’s tallest free-standing broadcasting tower; that Guinness World Records certified the tower as the world’s tallest tower on 17 November 2011; and that 634 was chosen because the digits sound out as Musashi, an old province taking in parts of Tokyo, Saitama and Kanagawa, which historical records place the site inside and which can be seen from the observation decks.
https://en.tokyo-skytree.jp/about/spec/
Tokyo Skytree — official page on structural design
Confirmed that the construction site was decided as the Oshiage district of Sumida Ward in 2006, that the tallest structure in Japan at that point was Tokyo Tower, completed in 1958 at approximately 333 metres and designed by Nikken Sekkei, and that the new tower is described as an attempt at nearly double that height approximately 50 years later; that a radiosonde weather balloon was launched to measure wind speed distribution and turbulence 600 metres above ground, and a microtremor array survey used to investigate the geology to about 3 kilometres down; that the foundation piles are wall-like with knuckles to increase frictional resistance, connected and spread radially, and continuously joined to the above-ground steel frame; that the first above-ground steel column, photographed on 6 April 2009, was approximately 4 metres high, 2.3 metres in diameter, 10 centimetres thick and approximately 29 tons; that high-strength steel pipes of about twice standard strength were used, with base pipes 2.3 metres in diameter and 10 centimetres thick; that the frame is a truss joined by branch joints welded directly without plates; and the whole account of the vibration-control system, including the structurally separated reinforced concrete cylinder with an internal emergency staircase, its upper part acting as a weight, the mass addition mechanism, the reduction of response shear force by about 40 per cent in a major earthquake, the claim that this is the world’s first use of a central shaft containing a staircase as the added mass, and the statement that five-storey pagodas have collapsed from typhoons and fire but have no record of collapsing from earthquakes.
https://en.tokyo-skytree.jp/about/spec/structure/
Tokyo Skytree — official outline page
Confirmed that the tower was built in 2012 as the world’s tallest free-standing broadcasting tower; that the foot is triangular with each side approximately 68 metres and that three points are described as the smallest stable unit; that the steel framework including the observation decks weighs approximately 36,000 tons; that the Tembo Deck holds approximately 2,000 people and the Tembo Galleria approximately 900; that four lifts run from ground level to the Tembo Deck at 600 metres per minute in approximately 50 seconds and two run from the Tembo Deck to the Tembo Galleria at 240 metres per minute in approximately 30 seconds; that the Tembo Deck is at floor 350 and the Tembo Galleria is a sloping walk from floor 445 to floor 450 where the highest point sits, with the digital broadcasting antenna above at 634 metres; and that the operating company is TOBU TOWER SKYTREE Co., Ltd., with Nikken Sekkei Ltd. as design and supervision office and Obayashi Corporation as constructor. Also confirmed the address at 1-1-2 Oshiage, Sumida-ku, 131-0045, and the four named research organisations using the tower as a research site.
https://en.tokyo-skytree.jp/about/outline/
Tokyo Skytree — official page on its role as a broadcasting tower
Confirmed that the main role is the transmission of terrestrial digital broadcasting; that terrestrial digital broadcasting began in the Kanto region in December 2003 and that numerous 200-metre-class skyscrapers in the city centre could affect radio wave transmission; that a 600-metre-class tower approximately doubles the transmission height and was expected to widen the coverage area of One-Seg, which began in April 2006; that the tower is expected to serve as a disaster-prevention tower; and the project history in full, from the December 2003 launch by six Tokyo-based television companies, the December 2004 request to Tobu Railway and its February 2005 announcement, the March 2006 site selection in the Sumida and Taito area, the December 2007 reservation agreements, the June 2008 name decision and July 2008 start of construction, the December 2008 TOKYO MX agreement, the April 2012 start of FM radio for NHK and J-WAVE and of the taxi radio system, the October 2012 TOKYO MX simulcast and its May 2013 completion, the May 2013 start by NHK, Nippon Television, TV Asahi, TBS Television, TV Tokyo and Fuji Television, and the December 2015 start of FM complementary broadcasting by TBS Radio, Nippon Cultural Broadcasting and Nippon Broadcasting System.
https://en.tokyo-skytree.jp/about/role/
Last updated: October 2026
