The Pyramids (Indianapolis) USA

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The Pyramids are three pyramid-shaped office buildings that are part of a 200-acre (810,000 m2) commercial development in College Park, Indianapolis, Indiana, USA. Each tower is made up of two walls of reinforced concrete from which project the unobstructed office floors. Those concrete walls provide the support for the floors as well as serving as L-shaped service cores. The other two walls are covered in blue exterior glass and each building is connected to the others via underground and above-ground passages. [Wiki]