Established in 1975 and based in Rotterdam, Office for Metropolitan Architecture (OMA) is headed by Rem Koolhaas. The firm specialises in architecture, urbanism and cultural analysis and has a research studio called AMO.

Pictured above is CCTV Headquarters in Beijing – two towers that lean towards each other, bridged at the the top and bottom to form a distorted loop.

Locations: Rotterdam, New York, Beijing, Hong Kong, Doha, Dubai and Australia

Number of employees: 200-500
Website: www.oma.eu