Fundamental Architects in the The Netherlands offers a rather unusual take on the high-rise with its Tower of the Sun concept. The eye-catching design is defined by a large circular hole at its center and would feature significant sustainable technology, drawing energy from the river it bridges.

If built – and, to be clear, there are no immediate plans to do so – the mixed-use high-rise would reach a height of 121 m (396 ft) and bridge the river Ishim in Astana, Kazakstan, with its 75,000 sq m (roughly 807,300 sq ft) of floorspace taken up by residential, office, hotel, and commercial areas. The overall design, which brings to mind the Guangzhou Circle Mansion, is inspired by traditional Kazakh culture.

"The ideas and symbolism of Kazakh culture and traditions are deeply intertwined in the concept of the project on every level, starting from the circular opening in the center of the building symbolizing the Sun, Peace and Unity – a symbol of core importance in Kazakh culture, to the triangular elements in the structure and interiors, which represent a powerful personal mascot that can be usually found in the traditional jewelry and clothing," says Fundamental Architects.

The ground floor would host a pedestrian and bicycle bridge joining parks either side of the river. A shopping mall would be situated above and two triangular lobbies on either side of the circular opening's base would serve as the main entry points for the residential and mixed-use wings of the tower. The building would be topped by a publicly-accessible terrace.

The Tower of the Sun concept also calls for ambitious sustainable technology and would make use of the river below.

"The project celebrates near net-zero energy requirements by using the power of water stream in the river underneath," adds the firm. "It doesn't require a typical dam for creation of hydroelectric power, but introduces a narrower river cross section under the building to increase the stream speed and its power. Heat pump and smart building orientation which avoids overheating of the building from the south-western side during hot summer days maximizes the efficiency of the building."

The Tower of the Sun is the result of an architecture competition held for BI Group, a developer in Kazakhstan, and also involved Omega Render.

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