20 years ago, a major discovery was made at Clifton Suspension Bridge in Bristol.
Contractors found secret vaults hidden below the iconic structure designed by Isambard Kingdom Brunel.
At the time it was thought that the amazing spectacle would never be available for public viewing but now those very vaults are part of a tour run by the Clifton Suspension Bridge Trust.
ITV reporter Rebecca Broxton reported on the discovery back in 2002 but never thought this day would come to pass.
She said, "Despite the beauty of the vaults, with their 13 feet long stalactites and stalagmites, it's unlikely the public will ever get to see them.
"The shafts are too narrow and it's too dangerous."
Watch Rebecca Broxton's report on the discovery below the bridge tower
Specialist equipment was needed to access the structure and clear tunnel entrances filled with rubble left by the original workforce more than 150 years ago.
Now a platform has been installed in the largest and most significant of 12 stone chambers – an echo chamber, 11m high, full of stalactites. It means families can see the spectacle for themselves.
Laura Hilton from the Clifton Suspension Bridge Trust said, "It's something that only a few people get to see.
"A lot of people when they visit the bridge they don't even know that it's there and they can be standing right on top of it. It's underneath their feet and this amazing space like nothing you've ever seen before. It's just right underneath you. It's very exciting,"
The family-friendly 'Vaults Visits' are selling fast, alongside special 'Hard Hat Tours', and the Trust is having to add new dates to keep up with demand. The trips will run until the end of October.
People can find out more about this wonder of Victorian engineering - and book tickets - on the Clifton Suspension Bridge website.