The best tall buildings in the world for 2014 unveiled

The winning buildings are from the USA, Australia, the Netherlands and the United Arab Emirates, and one of the four will be named overall winner for the "Best Tall Building Worldwide" this November.

Winner in the Americas was the Edith Green-Wendell Wyatt Federal Building in Portland, Oregon -- an 18-storey, 512,474 square-foot (47, 610-square-meter) office tower, completed in 1974, which recently underwent major renovation work by Cutler Anderson Architects, Sera Architects and Howard S. Wright Construction. A distinctive shading façade has been added to the structure, transforming the building from a bunker-like, concrete-encased mass into a lightweight trellised volume which is much more energy-efficient.

One Central Park in Sydney by Jean Nouvel won the Asia and Australia category for its unusual technological features -- hydroponics and heliostats -- which are used to grow plants around the periphery of the building at all levels. The shading saves cooling energy, while the heliostat directs sunlight for heating and lighting into or away from the building and the adjoining park when it is most needed.

In Europe it was the De Rotterdam by Rem Koolhaas's firm OMA which won the title. The largest building in the Netherlands features different light programs which lend dynamism and contribute to the humanization of the monoliths.

The final winner was the Cayan Tower, Dubai, by SOM, which came top in the Middle East and Africa category. The 75-storey luxury apartment building features a striking helical shape, turning 90 degrees over the course of its 304-meter (997 foot) height. Each floor is identical in plan, but is set 1.2 degrees clockwise from the floor below, giving the tower a distinctive form.