It has been hidden from the public for over 50 years.
But soon, commuters who use Peckham Rye station will be able to see inside the regal waiting room and south wing stairwell built in the 1930s.
A group of architects and local historians are working on the second floor room, which closed in 1961, to return it to its former glory.
Only accessible via Platform 3, the waiting room - located above the ticket hall - is large enough for over 100 commuters to take shelter.
It was designed by Charles Henry Driver, also the architect of Denmark Hill and Battersea Park, and a number of the great pumping stations built London’s sewage system.
The renovation is the latest project for Benedict O'Looney Architects at the 150-year-old station.
The firm has already renovated the 'Sanitary Courts' rediscovered after work began on the station forecourt in 2012, complete with green and white glass mosaic floors.
Architect Benedict O'Looney, who has been fundraising for the restoration for eight years, said that only the Gents is still intact after the ladies were demolished by accident in 2010 by Network Rail.
When we found our way in with the lights of our mobile phones, we found this incredible glass mosaic floor so it is something like a Pompeian discovery for us local architects. And then as we made our way deep into the space we found the Sanitary Courts which is still largely intact, capable of restoration and these wonderful traces of life, occupation, a hubbub of activity.
The team has cleaned and restored the Jesse Rust's patent glass mosaic, restored the original sanitary ware and fittings and even conserved the ironmongery and World War II venereal disease notices.
The project was shortlisted and highly commended in the National Railway Heritage Awards 2014.
The renovation had to include hand-basins, worryingly missing from the Gents toilets, so that the newly refurbished Sanitary Courts can return to use as part of a restaurant due to open on the ground floor of the building.