Staff and visitors will be welcomed to the building by a skylit atrium offering views into the four levels of glass-fronted workspaces above. A 4,000-square-metre triple height "hub" at the centre of the building will house studios, offices and production facilities.
When it opens, the headquarters will include a range of administrative spaces and production studios, as well as a ground-level cafe facing the square and a restaurant on the roof.
"The design of the building is inspired by its unique location and the institutional heritage of the BBC, to create a distinctive icon that the people of Cardiff can be proud of," said head of studio at Foster + Partners, Gerard Evenden.
"A progressive, state-of- the-art workplace for the BBC, it also forms the central focus for the regeneration of this urban quarter, and we look forward to its full opening next year."
Developer Rightacres is overseeing the regeneration project, which will including another project by Foster + Partners – Two Central Square. This building will become home to Cardiff University's School of Journalism and Hugh James Solicitors.
A curved opening in the metal roof plane allows natural light into the roof garden, which offers views across the city and provides a spot for outdoor filming.
The design's environmentally friendly features including chilled beams, and use of local and recycled materials, have earned the building an "outstanding" accreditation from sustainability assessors BREEAM.
The building's mechanical systems are organised to offer a flexible layout, helping to future-proof the building against the advent of new broadcasting technology.
Foster and his firm came in at number nine on the lastest Dezeen Hot List, a comprehensive guide to the hot topics and key figures in the architecture and design world over the past year.
Foster is currently working on a broad range of projects. Recently he collaborated with Rapha to design a range of cross-country ski wear, and his firm is designing a new headquarters for golfing association PGA Tour in northeast Florida.
Photography is by Nigel Young.