While the construction of towers isn’t necessarily one of the major challenges of the 21^st century, urban growth is: soon, 70 % of the world’s population will be living in an urban environment. Towers can occasionally meet the stakes of mobility, attractiveness and diversity, used as an argument for the development of more sustainable cities. This is what Claire Saint-Pierre, a young researcher from the University of Liège, studied in her thesis.

Height has always been a symbol of prestige. In biblical texts, the Tower of Babel reached the heavens. And then there are other well-known towers: Eiffel, Pisa, Big Ben... and, more sadly, the twin towers of the World Trade Center. Since the beginnings of urban society, the status and role of tall buildings have evolved significantly. Until the end of the 19th century, towers were the exclusive reserve of a higher power, whether political or religious. The 20th century marked the arrival in North America of the first inhabitable towers intended for the tertiary sector. These skyscrapers were the symbol of a group's economic power. The race for height and innovation had begun. Now, these steel and glass colossi dominate all the world’s biggest cities, like a form of acceptance of the capitalist ideology, symbolising more than ever a nation’s strength and modernity.

The lowdown on the tower

Towers have existed for centuries and their purpose has evolved considerably: sometimes used for surveillance or defence, sometimes the symbol of religious or governmental power, sometimes used for telecommunications, sometimes for trade or residential purposes. The terminology of the word ‘tower’ is also variable. According to France’s ‘Centre National de Ressources Textuelles et Lexicales’, the basic definition of a tower is “a building whose height is much greater than its breadth, dominating a building or an architectural complex, and whose role is generally defensive”.  Other terms may be gradually created when new morphologies and new functionalities appear. “In law and in the domain of construction, we usually talk about tall buildings, or high-rise buildings (HRB), when these constructions are inhabited. The term ‘skyscraper’ appeared at the beginning of the 20th century in the US. In any case, it is the ratios concerning height that are important: a vertical scale far greater than the horizontal scale and height of the tower relatively greater than that of the surrounding buildings. Nowadays, high-rise buildings are also characterised by their technology", explains Claire Saint-Pierre, author of a doctoral thesis on the subject (1) and member of the University of Liège’s ArGEnCo department.

The word ‘skyscraper’ inevitably makes us think of New York, or of the classic layout of the Central Business Districts (CBD) in big American cities. When it comes to seeking the public's opinion on the building of a new tower, the answer will vary greatly according to the geographical area. “Towers are generally more accepted in America and Asia than in Europe. The United States are the cradle of skyscrapers and high-rise buildings. They enabled significant progress in urban development in the 19^th and 20^th centuries and people there are more accustomed to this urban morphology. In Europe, towns generally have more historical or listed buildings and it is more difficult to make radical changes in town centres. Especially in France, where people still have bad memories of the towers built in the 1970s. Since then, people have found it hard to accept towers, particularly the local residents of a future tower project”, says the researcher native to the suburbs of Paris.

(1) Diagnostics de sites et méthode d’implantation de tour pour une insertion urbaine de qualité. Claire Saint-Pierre, doctoral thesis written under the direction of professors Jacques Teller and Youssef Diab, University of Liège, 2014, 483p.