(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.

Protecting London's landmarks

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.

Photos: View from the top – The Shard -- seen here at sunset -- towers over London's skyline. More than 430 new tall buildings are currently in various stages of planning for the UK capital. Critics worry these buildings damage -- rather than improve -- the aesthetic appeal of city's skyline. Hide Caption 1 of 17 Photos: The changing face of the city – Prior to the 20th century, London's St Paul's Cathedral was the architectural focal point of the city. This image from 1616 depicts the South-west prospect of London from Somerset House to the Tower. St Paul's Cathedral is the tallest building for miles around. Hide Caption 2 of 17 Photos: The advent of the skyscraper – The 209-feet Senate House, built in 1937, was London's first skyscraper. Writer George Orwell supposedly modeled 1984's tyrannical Ministry of Truth on the now-iconic London building. Hide Caption 3 of 17 Photos: The changing face of the city – London's skyline was irrevocably altered by bombing in the Second World War. Many of the remaining historical buildings became protected -- but whole areas were wiped out and needed to be rebuilt. This image depicts St Paul's post-war reconstruction being carried out in London after the war. Hide Caption 4 of 17 Photos: London's race to the top – At the beginning of the 21st century, London began to build skywards. Recent skyscrapers such as the Cheesegrater, the Gherkin and the Walkie-Talkie are now all key features of the London skyline. Hide Caption 5 of 17 Photos: The juxtaposition of the old and the new – Today, London's skyline juxtaposes the old and the new. Here the Leadenhall Building -- known as the "Cheesegrater" -- leans sideways to avoid blocking St Paul's Cathedral. Hide Caption 6 of 17 Photos: The Eastern Cluster – The majority of London's extreme skyscrapers -- such as One Canada Square, Heron Tower and the Gherkin -- are located in the "Eastern Cluster". Hide Caption 7 of 17 Photos: The changing face of the city – The Cluster is home to buildings such as 30 St Mary's Axe, nicknamed the Gherkin, which was initially ridiculed by Londoners but has since become a quirky staple of the city's skyline. Hide Caption 8 of 17 Photos: London's future skyline – Londoners are now complaining that proposed super-tall building 22 Bishopsgate -- the construction site of which is seen here -- would block views of the Gherkin, towering over its neighbors' 180m at 262m. Hide Caption 9 of 17 Photos: Room with a view – The Shard -- Britain's tallest building -- contains offices, a hotel and luxury apartments, and was billed as a "vertical city". The building attempts to appeal to Londoners and visitors alike with its View From the Shard experience. On the top two floors of the building visitors can admire spectacular 360 panoramas of the city. Hide Caption 10 of 17 Photos: Iconic views – London's skyscrapers compete with iconic buildings such as Tower Bridge in the most beloved building polls. "Buildings gain importance and lose importance," says Annie Hampson, current City of London planning officer, "One has to accept that views do change". Hide Caption 11 of 17 Photos: London's housing crisis – Critics of tall buildings argue they do nothing to aid London's housing crisis. Hide Caption 12 of 17 Photos: Skyscraper city – London is building upwards in part to compete with cities such as Dubai. The Middle Eastern city has 911 completed high rises and is home to Burj Khalifa -- the tallest building in the world -- seen here towering over the city's skyline. Hide Caption 13 of 17 Photos: A vision of the future? – The Burj Khalifa soars 828 meters into the sky. But even the Burj is soon to be overshadowed by the Kingdom Tower in Jeddah, Saudi Arabia -- a skyscraper likely to reach one kilometer high. Hide Caption 14 of 17 Photos: The competition continues – Once completed in 2020, the Kingdom Tower in Jeddah, Saudi Arabia, is likely to set new records for height at one kilometer high. Hide Caption 15 of 17 Photos: Race to the top – Skyscrapers in Shanghai symbolize a shift in global power dynamics. Here, the Shanghai World Financial Center is viewed from the Shanghai Tower -- the second tallest building in the world. Hide Caption 16 of 17 Photos: Futuristic cities – Shanghai's ever-growing skyline is a symbol of China's status as a burgeoning global power. London continues to build upwards in an attempt to keep up with new global powers. Hide Caption 17 of 17

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".

A gentleman's agreement

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.

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This voluntary approach proved to be surprisingly successful in protecting important views during the post-Second World War reconstruction of the City of London.

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.

Eight wonders of the city

Can London deliver enough accommodation while still protecting these views? Annie Hampson, the City of London Planning Officer

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.

Photos: London in miniature – New London Architecture (NLA) is an independent forum for discussion about architecture and planning in London. The NLA Galleries -- based at The Building Centre in the center of the capital -- tell the story of London's development through exciting permanent and temporary exhibitions. Hide Caption 1 of 6 Photos: London in miniature – The NLA's permanent exhibition includes a 1:2000 scale interactive model of central London. Hide Caption 2 of 6 Photos: London in miniature – There are eight protected view corridors -- converging on St Paul's Cathedral -- where tall buildings are prohibited. These lines can be projected on the NLA Model. Hide Caption 3 of 6 Photos: London's future skyline – There are over 430 tall buildings in the works for London. Any project under construction or with planning permission can be highlighted on the model with 3D-printing technology. Hide Caption 4 of 6 Photos: London in miniature – At 12.5 metres-long, the model covers more than 85 square kilometres of London,19 Boroughs and approximately 170,000 buildings. Hide Caption 5 of 6 Photos: Interactive London – The model illustrates London's architectural development through detailed artistry, projections and interactive films. Hide Caption 6 of 6

Exceptions to the rule

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]".

Primrose Hill offers a panoramic view of the London skyline

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.

The view forward

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."

King Henry VIII's mound is situated 10 miles from St Paul's.

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.