Tourists are paying to be given guided tours or underneath Britain's busiest motorway junction.
People have the opportunity this week to go on an organised two-mile walk beneath Birmingham's Spaghetti Junction - for £10 per head.
The winding labyrinth of roads along the M6 is one of the biggest motorway interchanges in Europe and more than 200,000 vehicles travel on it daily.
The iconic 52-year-old concrete structure even appears in the Guinness Book of World Records as "the most complex interchange on the British road system'.
People are now being invited to get a rare and unique look underneath the twisting five levels of motorway lanes which make up the Gravelly Hill Interchange.
For £10, punters can enjoy 45 minute tours exploring canals, rivers, a park, a lake, towpaths, wildlife, street art - and even 'a beach'.
Organisers Explore Birmingham said: "This walking tour takes you to a startling and unique space few people seek out – underneath the Gravelly Hill Interchange aka Spaghetti Junction.
"Famous (and infamous) across the UK, it’s one of the best known landmarks in the city.
"Its tangle of roads can strike fear into wary drivers and it often holds a dark place in the psyche of the city, but is this a misunderstood beast?
"Thundering high above our walking route are the roads of one of the UK’s most complex pieces of road infrastructure.
"Below is an exhilarating space of canals, rivers, a park, a lake, towpaths, wildlife and street art.
"It may not be conventionally pretty, but this gritty, urban underworld has a unique atmosphere which you have to experience to appreciate. A must for photographers.
"Old canal architecture is strikingly juxtaposed with modern road infrastructure, much of it covered in street art.
"It truly feels like entering another world. Sometimes described as dystopian, the spaces created have provided the backdrop for art exhibitions, dance events and films.
"The tour explores the legacy of this extraordinary monument, now over 50 years old, the story of its construction, how it shattered communities and inspired others."
Spaghetti Junction was opened in 1972 and took some four years to complete at a cost of £10 million.
It has 559 concrete columns - some reaching 80 feet high - is reinforced by 13,000 tonnes of steel and covers an area of 30 acres.
If you wanted to drive along every road at Gravelly Hill Interchange, you would need to travel about 73 miles and it also serves 18 different routes.
Tour guide Al Hassall told the BBC: "It's an unusual space but one with a wealth of history.
"Many people have wondered what it is like to go down but people don't know necessarily how to get down and whether it would be safe once they do.
"Coming on an organised tour has been great for people to have the chance to see what's underneath."
Architecture expert Dr Michael Dring added: "It's a wonderful structure. It was designed as an image of the future for the city.
"It engages with the landscape and introduces people into the city so it does have its own beauty."
The guided tours are being given this week as part of Birmingham Heritage Week and conclude on Sunday (15/9).
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