Dragon's Den production moved to Salford when the show relocated to MediaCityUK.
MediaCityUK is a large mixed-use development in Salford, Greater Manchester, built around media, broadcasting and creative industries. The BBC became a major tenant there, and Dragon's Den was among the programmes associated with the move of production from London.
Salford is a city in its own right, although it forms part of the wider Greater Manchester urban area and sits immediately across the River Irwell from Manchester. That geography is why the location is sometimes loosely described as Manchester in general conversation.
The answer is therefore Salford rather than Manchester, the nearest famous city name. MediaCityUK's presence also explains why several national BBC productions became linked with Salford during the corporation's broader relocation of departments and studios.