(CNN) Tucked away in a residential corner of south-east London, Blackheath Park is neither well signposted nor easily located on a map.
Yet this tourist non-spot has an incredible asset -- a strikingly unspoiled view of central London, spanning many of the city's iconic landmarks from the gleaming 21st century Shard to St Paul's Cathedral, built in 1675.
Only a few cranes encroach on the view.
But this pristine panorama is no accident.
Blackheath Park is home to one of London's eight protected views of St Paul's Cathedral, a series of visual corridors that have been quietly safeguarded since the 1930s.
The London Building Acts of 1888 and 1894 ruled that architects should not be allowed to build structures in London higher than a fireman's ladder -- roughly 10 stories -- to ensure the city's finest landmarks, specifically St Paul's Cathedral, were not overshadowed or obscured.
This rule was not amended until 1956.
In the 1930s, however, skyscrapers taller than this began to shoot up in New York City, signaling a new era in architecture.
Across the pond in London, developers of buildings such as Unilever House (1933) started to skirt the London Building Acts by claiming the top floors of their towers were not for office or residential use.
Amid pressure from developers to be allowed to build taller buildings, in 1938 the City of London Corporation introduced London's "protected views" system -- to allow controlled construction that would not obscure views of St Paul's Cathedral.
Architect W Godfrey Allen, an adviser to St Paul's on the structure and setting of the cathedral, plotted multiple views of the iconic building from various vantage points in the city.
Allen outlined eight "protected view corridors".
Allen's proposals were accepted by the City of London Corporation, and implemented in 1938 -- upheld by a "gentleman's agreement" (an arrangement or understanding based upon the trust of all parties, rather than being legally binding) between the City Corporation and developers.
This voluntary approach proved to be surprisingly successful in protecting important views during the post-Second World War reconstruction of the City of London.
Similar rules protecting views of -- and from -- the 17th century Monument to the Great Fire of London, The Tower of London and Thames river vistas were implemented later in the 20th century.
In the 1980s, protected views were given policy status in statutory development plans, and are currently implemented through the City of London's Core Strategy -- a framework for guiding development until 2026.
Aside from Blackheath, London's seven other protected corridors radiate from: North London's Alexandra Palace; two vantage points in Hampstead Heath (Parliament Hill and the stately home Kenwood House); Primrose Hill has another spot, 63 meters above sea level; Greenwich Park's General Wolfe Statue; Westminster Pier; and King Henry VIII's mound -- over 10 miles (16 km) away from St Paul's Cathedral and only visible through a cultivated gap in a hedge.
While Londoners would likely agree that these panoramas are impressive -- and Primrose Hill, Alexandra Palace and Hampstead Heath are well-known viewing spots -- few realize that the fine panoramas are protected.
While the eight protected views of St Paul's have survived since the 1930s, some exceptions have been made.
The Shard -- the UK's tallest building and the tallest in Western Europe -- for example, is situated in the Kenwood House viewing corridor.
Gwyn Richards, the City of London's head of design, tells CNN that when proposals are suggested for new buildings, the viewing corridors always come under consideration.
"It would be difficult to argue that you could breach the foreground of the view," says Richards, "But there's more of a debate to be hand when buildings breach the background. You need to assess whether or not that proposal affects your ability to see [St Paul's]".
The Shard exists in the background area of the Hampstead Hill viewing corridor.
Developers and London officials had to make a judgment call as to whether or the Shard's presence would impede views.
After much debate, it was considered acceptable.
So, The Shard dominates the vista from Parliament Hill and Kenwood House -- not blocking the view, but certainly changing it.
Some experts, however, are beginning to question whether city planners should be protecting views of St Paul's in the 21st century.
Is Sir Christopher Wren's hallowed dome really more important than other modern landmarks, or London's need for development?
Annie Hampson, the City of London Planning Officer -- whose role shaping London's landscape lead her to be named by the London Evening Standard one of the "most influential people in London" -- tells CNN that buildings "gain importance and lose importance" throughout history.
She cites as an example 30 St Mary Axe, aka the Gherkin. Widely derided when finished in 2003, today, Hampson says, "some people have begun to see the Gherkin as an important London landmark. One has to accept that views do change."
Are views of the Gherkin less worthy of protection than those of St Paul's?
"Some people say these (protected) views act as a constraint on development, can London deliver enough accommodation while still protecting these views?" she adds.
Architect Barbara Weiss, founder of the Skyline Campaign -- a pressure group that lobbies against the onslaught of tall buildings in development in London -- deems the protected view corridors out of date and elitist.
"They are very anachronistic, an expression of the class system. Certain views are protected from certain angles but from South London much less so," Weiss says, noting that the viewing corridors tend to emanate from wealthier parts of London.
Others are in favor of keeping the corridors.
"I believe protected views are helpful in providing a constraint that aids development," explains Peter Wynne Rees, the former City of London City Planning Officer, "but you can't protect every view of everywhere".
One thing is clear: on a crisp, sunny autumn afternoon, Primrose Hill is packed with locals and tourists alike -- taking photographs, picnicking and admiring the iconic London vista.
They might not know that it's protected, but they are certainly enjoying the view.