The gym is situated underneath Broadgate Circle, an open-air dining and shopping area in east London, and is the second branch for new fitness company 1Rebel.
Inspired by the subterranean location, Studio C102 decided to create a space with a "dark and moody" atmosphere while using materials inspired by contemporary art and design.
"The brief was to design each new 1Rebel gym to look as individual as possible while still keeping to the brand promise of every class feeling like a night out – an event in its own right rather than a means to an end," said Studio C102 founder Kyriakos Katsaros.
"By responding imaginatively to the differences in the site, we have created a distinct sense of place," he added.
"At the same time we have maintained a constant design language and overall palette of materials that draws inspiration from contemporary art and cutting-edge retail design, rather than the fitness sector," he continued.
Visitors access the gym at street level, and a staircase leads them down to a retail space and reception area.
Here, Kee-Klamp railing – structural pipe fittings commonly used for handrails and barriers – is used to display iPads and clothing before climbing over the reception counter to create benches.
Stark white tiles cover the reception desk, while black tiling was used to form a small pop-up juice bar. The gym's logo is displayed on the wall in blue neon lettering.
Aiming to reaffirm the nightclub theme, the architects completely covered both studios within the gym in black-painted timber panels and black rubber flooring.
Rumble, a studio space dedicated to high-intensity training, is circular shaped and features rows of custom-made punchbags hanging from the concrete ceiling.
"In the Rumble studio, the circular space has been accentuated," said Katsaros. "It sits directly under the Broadgate circle, and the placement of the custom made boxing bags and theatrical lighting creates a unique space for 1Rebel's HIIT sessions."
A second studio filled with treadmills and weights curves around the outside of the Rumble space and features steel-framed mirrors made from Georgian wired glass.
Both male and female changing rooms contain bulb-lit mirrors, galvanised steel lockers and fridges containing towels. Copper showers are concealed behind brass-framed glass doors.
Photography is by Gareth Gardner.