Case Study: The Parametric Twist of Canton Tower

The parametric twist of Canton Tower comes from one simple rule: two ellipses, one at the foundations and one at about 450 m, are rotated against each other, and straight inclined columns joining them produce the tower’s narrow “waist”. This case study is for architecture students and designers interested in computational design. It explains what the tower is used for, how Information Based Architecture (IBA) and the engineers Arup turned that rule into a buildable lattice, and then walks through the method step by step so you can reproduce the logic on a model of your own.

TV towers are usually imagined as antennas on hierarchical lattice frames. The Canton Tower in Guangzhou, designed by Mark Hemel and Barbara Kuit of IBA, is one of the best-known towers whose whole form is generated from a few geometric parameters.

What is the Canton Tower used for?

The tower stands in Guangzhou’s Haizhu district where the city’s new central axis meets the Pearl River, China. Completed in 2010 in time for the Guangzhou Asian Games, it is a broadcasting and sightseeing tower: it carries television and radio antennas and holds observation decks, restaurants, exhibition spaces and visitor attractions. The CTBUH’s Skyscraper Center lists it at 604 m to its tip, with an occupied height of 448.8 m, and classifies it as a telecommunications and observation tower rather than a building, because less than half of its height is usable floor area.

Its twisting form invites comparison with Shanghai Tower; our case study of Shanghai Tower explains how BIM was used to deliver that building.

1. Building background

The design was chosen through an international competition in 2004, which IBA, then a young Amsterdam practice, won against larger, established firms. The brief covered not only the tower but also the surrounding park and a wider master plan. IBA’s concept was a tapered, twisted elliptical tower, conceived as a slender “female” counterpart to the straight, repetitive forms of most towers. Its pinched waist earned it the popular nickname “Xiao Man Yao”, roughly “slim waist”, as the tower’s history records.

The main tower rises to a top deck at about 454 m, and the antenna mast extends about 146 m further, for a design height of around 600 m (604 m as measured by the CTBUH). The programme is spread through the height in three broad zones:

• Base: entrances, connections to public transport and parking, visitor facilities, shops and the lift lobbies.
• Middle: visitor attractions, restaurants, cafés and outdoor terraces around the narrow waist.
• Top: technical equipment, including the damping systems that limit sway, restaurants, an indoor observatory and an open-air deck.

2. Building context: a tower for visitors

IBA wanted an unfamiliar geometry for a TV tower and a structure that invited people in. The most direct expression is the Spider Walk, an open-air staircase of 1,028 steps between floors 32 and 64 that climbs through the waist, letting visitors see the lattice from inside. At the top, the outdoor deck at 488 m opened in late 2011; around its edge runs the Bubble Tram, a ring of transparent cabins circling the tower at about 455 m, and a free-fall ride called the Sky Drop starts at about 485 m, according to visitor guides to the tower.

3. Overview of the parametric design

Hemel and Kuit set out to design a tall, free-form and asymmetrical tower that would look “in movement” rather than static, as a symbol of a dynamic city. Hemel has credited parametric associative software with making the complex geometry possible: once the generating rule was set, every column, ring and brace could be derived and adjusted from a few inputs rather than drawn one by one.

Software did not produce the parametric twist of Canton Tower on its own. Parametric tools let the architects and Arup test variations quickly, pass consistent geometry to structural analysis and produce the data that fabricators needed for thousands of differing elements.

4. The geometry

The form, volume and structure are generated by two ellipses: one at foundation level and one on a horizontal plane at about 450 m. Rotating the upper ellipse relative to the lower one and joining them with straight lines produces a surface that tightens in the middle. This is the parametric twist of Canton Tower in its simplest form: the tighter the rotation, the slimmer the waist and the denser the structure there. The client encouraged the designers to make the waist as slender as possible, which became the main technical challenge: the narrow middle still had to hold the core with its lifts and stairs and to carry the loads of the floors above.

Once the surface was fixed, it was converted into a three-dimensional wireframe for structural analysis and resolved into three element types: columns, rings and diagonal braces meeting at nodes. Because the surface is double-curved and asymmetrical, the elements and nodes vary in size and angle around and up the tower.

5. The structural design

The structure is a tube within a tube. The inner tube is an elliptical reinforced concrete core that contains the lifts, stairs and service shafts and carries the floors. The outer tube is the steel lattice, which Arup describes as a triangular lattice of concrete-filled columns, rings and diagonal tubes wrapped around the core.

• Columns: 24 inclined steel tubes filled with concrete run from the base to the top. Published figures give a diameter of about 2 m at the base, reducing towards the top; sources differ on the exact upper diameter. The concrete infill adds stiffness and fire resistance.

• Diagonals: steel tubes that cross the columns to form the triangulated lattice and give the outer tube its shear stiffness.
• Rings: 46 elliptical steel rings, each set at an angle of about 15 degrees to follow the twisting form, tie the columns and diagonals together around the tower.

• Nodes: where columns, rings and braces meet, every node differs in geometry, which made node design and fabrication one of the project’s main challenges.

6. The antenna

From the top deck at about 454 m, a steel antenna mast rises about 146 m to the tip. It carries the broadcasting equipment and gives the tower its overall height of around 600 m.

7. Fabrication and construction

Because the surface is curved and asymmetrical, very few structural members repeat, so every piece needed its own geometry and setting-out data. The steel members were prefabricated, delivered to site and erected piece by piece around the rising core; the column tubes were then filled with concrete. More than 40,000 tonnes of structural steel were used, including the mast, according to Design Build Network’s project report.

The parametric twist of Canton Tower: a step-by-step method

The following worked example reproduces the logic of the tower in any parametric tool, such as Grasshopper for Rhino or Dynamo. It is a simplified, hypothetical study model with round numbers, not the real tower’s data, so you can see how each parameter changes the form.

1. Set two ellipses. Draw a base ellipse at height 0 and a smaller top ellipse at height H (for example 450 units). Make both radii, the height and the rotation angle into sliders.
2. Divide both curves. Divide each ellipse into the same number of points, for example 24 to match the tower’s columns.
3. Rotate the top ellipse. Rotate the top ellipse about the vertical axis by an angle θ. At θ = 0 the lines are simply tapered; as θ grows, the straight lines joining matching points begin to pinch together at mid-height and form a waist.
4. Draw the columns. Connect point i on the base to point i on the rotated top with straight lines. These are your inclined columns; together they define a ruled surface.
5. Add rings. Cut the surface with planes at regular heights to create rings. Tilt the planes slightly, as the real tower’s rings are tilted, and compare the effect.
6. Add diagonals. Connect each column-ring intersection to the next column one ring up to triangulate the lattice.
7. Measure the waist. Record the narrowest cross-section for several values of θ. Plot θ against waist width: this single chart shows why the client’s request for a slimmer waist made the structure denser and the core harder to fit.
8. Hand over to analysis. Export the lines as a wireframe for a structural analysis program, and list element lengths and node angles to see how many differ.

Diagram suggestion for each step: plan of the two ellipses with θ marked; elevation of the columns at θ = 0, 45 and 90 degrees; a section through the waist showing core and lattice. For tools to build the model, see our guide to architectural design software, and for another project driven by the same approach, our case study of computational design at the Hangzhou Tennis Center.

What the parametric twist of Canton Tower teaches

The lesson of the tower is not the twist itself but the method: a few clear parameters, a structural logic that follows the geometry, and data that runs straight from the model to analysis and fabrication. Try the method above with different rotations and heights, and you will see how one design rule can generate a whole family of towers.

Written by the Arch2O Internship Team; updated by Arch2O in October 2026.

Sources and further reading

• CTBUH Skyscraper Center, Canton Tower.
• Arup, China’s tallest tower opens.
• Detail, Canton Tower in Guangzhou.
• Design Build Network, Guangzhou TV Tower.
• Canton Tower, overview and history.