Viewers watching the first episode of new BBC Two series The City and The City may have already spotted several Liverpool streets and landmarks where the drama was filmed.
However, the show's producers also ventured underground in their bid to create the parallel-world dystopia inhabited by city-born actor David Morrissey and his assistant, played by Mandeep Dhillon.
One building in particular, the historic Cotton Exchange on Old Hall Street, provided a number of backdrops including a morgue and police station that were created in its vast two-storey basement.
The building's owner Bruntwood welcomed set designers and film crews from production company Mammoth Screen into the grade-II listed building for a number of weeks in April last year.
The next episode of the four-part series airs on Friday at 9pm on BBC Two.