SHANGHAI - Shanghai Tower, the world's second-tallest building, will soon open in the Chinese financial capital with a twist - a 120-degree twist, to be exact.

A softened triangular "outer skin" is literally twisted around a circular core, sending the glass and steel tower spiralling 632m into the grey sky above the city.

State-backed developer Shanghai Tower Construction and Development views the design as a symbol of China's future, a super-tall building in the city's gleaming Pudong financial district, which did not even exist 25 years ago.

People involved in the project said the building will open within the next three months, with office tenants moving in first, but the developer declined to comment.

"This twist is an iconic symbol of looking forward for the Chinese people," said Mr Grant Uhlir, practice area leader and principal for Gensler, the United States architecture firm whose design was chosen for the building.

Although still dwarfed by reigning champion Burj Khalifa in Dubai, which stands at 828m, the US$2.4 billion (S$3.2 billion) Shanghai Tower can still lay claim to a host of superlatives.

The tower, besides being the tallest double-facade building, will have the world's fastest lifts, travelling 18m a second, while the globe's second-highest hotel will sit on the 84th to 110th floors.

AGENCE FRANCE-PRESSE