Secret Worlds Hidden Beneath Surface Structures

Unusual, often puzzling, surface structures of many types can be found in our cities, towns and countryside.

Some ingeniously exploit their true purpose, becoming something aesthetic or eye-catching. Others affect a traditional disguise or are purely functional.

What they all have in common is that they are vital portals to subterranean worlds. They ensure, now or in the past, the proper functioning of infrastructure, tunnels, mines, secret bunkers and more, deep underground.

Here are 18 intriguing examples.

Concrete monoliths

Tyne tunnel

Two massive concrete ventilation shafts filter traffic fumes, keeping the air clean in the Tyne Tunnel: a pair of toll road tunnels (opened 1967 and 2011), nearly a mile long, running below the River Tyne.

The visually arresting shafts, inspired by the inverted cone-shaped chimneys of Venice, were designed by the architectural practice Ryder and Yates (now Ryder Architecture), influential Modernist pioneers in the North East of England from the early 1950s. Their work includes the Grade II* listed British Gas Engineering Research Station, Killingworth, Tyne & Wear (1966 to 1967), which has conical vents on its roof of similar design.

Camberwell Submarine

Reminiscent of a nuclear submarine, this concrete structure – designed in the 1970s by Lambeth Council architects Michael Luffingham and Bill Jacoby – houses the underground boilers that provide gas heating and hot water for the nearby housing estates; the two tall towers and the side vents acting as flues to keep the system cool.

It became obsolete in the 1990s when the area was regenerated with private housing but, after local controversy, the underground energy centre was refitted and modernised, including extending the original two chimneys upwards by 4 metres.

Blackwall tunnel

The first Blackwall Tunnel under the River Thames – linking Blackwall north of the river with the Greenwich Peninsular to the south – opened in 1897 for horse-drawn vehicles. 70 years later, a second parallel tunnel was built by the London County Council (LCC) to alleviate a huge rise in road traffic.

The two sensuously flaring ventilation funnels are made of sprayed concrete; their shape influenced by the pattern of aerodynamic airflow exhausted from giant fans. The taller tower vents vehicle pollution and the shorter draws in clean air.

They were designed by architect, Terry Farrell (1938 to present), then in his early 20s and working briefly for the London County Council; later internationally renowned for his work in the Far East and for designing the M16 headquarters in London’s Vauxhall and The Deep Aquarium, Hull.

Titans of brick, glass and stainless steel

Mersey tunnel

The Mersey Tunnel – running for a total of nearly 3 miles under the River Mersey at a depth of 45 metres, linking Liverpool with Birkenhead – was opened in 1934 by King George V.

Six massive ventilation stations were designed by celebrated Liverpool architect Herbert J. Rowse – three landmark structures of geometric Art Deco-style design each side of the river, housing duplicate giant blower and exhaust fans, up to 8.5 metres in diameter, which simultaneously draw out traffic fumes and deliver fresh air into the tunnel.

Blackfriars station

In 2012, Blackfriars Station was radically upgraded, becoming the only station in London whose platforms straddle the River Thames, with a ticket hall on both sides of the river. It parallels, and is close by, Blackfriars Bridge.

As part of the redevelopment, this towering shiny blue glass ventilation shaft, which pierces and rises above the roof, was installed to vent noxious air from Blackfriars underground station below.

In a world alive to the threat of terrorism, the specialist glass has been manufactured to absorb the blast of any underground explosion, potentially minimising injuries from flying shards of glass.

‘Angels’ wings’

The commercial redevelopment of Paternoster Square next to St Paul’s Cathedral was completed in 2003, having overcome a controversial intervention by the Prince of Wales who advocated traditional design over modern.

What looks like a silver sculpture has a hidden purpose. Made in two separate parts, with each ‘wing’ mirroring the other and composed of sixty-three identical triangles of stainless steel welded together, it is a vent for the electricity substation below ground. Hidden grills in the paving of the square draw down cool air to the substation, expelling hot air out through the two flues of the ‘Angel’s Wings’ above.

Relics of war

Second World War (1939 to 1945)

The Cabinet War Rooms in central London’s Whitehall, from where Churchill ran the Second World War, were highly vulnerable to air attack. This secret alternative bomb-proof bunker, 40 foot below the ground, was built in the far reaches of suburban London as an emergency standby for the War Cabinet should the Battle of Britain (10 July to 31 October 1940) have been lost.

After Britain achieved air supremacy in the Battle of Britain, the bunker was not required. Churchill visited just once, and it hosted only two meetings.

The extensive decaying subterranean bunker with its warren of rooms has remained largely untouched since the war. It is open twice a year to the public.   

Cold War (1947 to 1991)

The Cold War was a lengthy period of high global tension after the Second World War (1939 to 1945) – a geopolitical, ideological and propaganda-driven struggle for world dominance between the two nuclear superpowers: Capitalist USA and Communist Soviet Union and their respective allies.

RAF Kelvedon Hatch was developed in the early 1950s in response to a perceived Cold War threat when Britain feared nuclear air attack by the Communist bloc. It was one of several dozen radar and air defence stations, developed under the codename ROTOR, whose design blended in with local building styles:

This innocent-looking bungalow-like building is camouflage for a massive three-storey subterranean bunker. As a Sector Operations Centre, it could coordinate information from East coast radar stations and would be able to direct RAF fighter jets to confront the enemy.

Today, this former secret nuclear bunker is open daily to the public.

Thirty-four metres below this unremarkable structure in Manchester – one of several across the city – lie the enormous tunnels, maze of rooms, lifts and shafts of a highly secret nuclear-hardened bunker. Three such bunkers were constructed in England in the 1950s at the height of the Cold War, all designed to safeguard communications in the event of a nuclear attack. This bunker had its own self-sufficient water supply from an artesian well. There were sleeping quarters, a kitchen, and a bar with a piano and pool table.

The Exchange was decommissioned in the 1990s. The tunnels remain intact -reputedly used today by BT for cabling – but apparatus such as transformers, generators, communication equipment and ventilation controls have all been removed.

Decorative structures

Turkish bath house

This Islamic-style building was constructed between 1894 and 1895. Pictured is the entrance to the Turkish Baths, once occupying two subterranean floors, and in use until the 1950s.

Now an atmospheric events venue, the underground Bath House still features much of the original ornate, opulent, Islamic-style detailing – geometric motifs, multifoil arches, stained glass lights, niches with panels of interlocking tiles.

Historic stone tower

This unusual tower, with its now ruined top, is a flue for the former Wheal Exmouth mine deep below. It stands next to the restored three storey mine engine house (listed Grade II), now a private home.

The Teigh Valley where the shaft and engine house are located had upwards of 200 mines in the 19th century, producing ores of lead, silver, zinc, copper, tungsten and arsenic. In its heyday, Wheal Exmouth – operating from the 1850s until around 1880 when the mine was worked out – employed 70 underground workers.

The buildings’ ornate style may be because the mine was originally visible from Canonteign House (built in 1828 and listed Grade II), seat of the Viscounts Exmouth, and the family wanted a more aesthetic outlook.

Eduardo Paolozzi sculpture

The period after the Second World War saw a shift from commemorative sculpture to the ideology of enhancing the public realm through art.

Edinburgh-born Eduardo Paolozzi (1924 to 2005) was one of Britain’s foremost artists during the second half of the 20th century. His work in the 1950s was often inspired by machinery and other moving parts, and he collaborated with industrial engineering firms.

The pictured 12 metre high ventilation shaft – which vents emissions from the underground car park deep below – was commissioned by the Crown Estate Commissioners and installed in 1982.

Each of the robotic-feeling sculpture’s four lower steel panels features irregularly cast, stylised images of mechanical parts of machinery, plus geometric shapes, insects, fish and clocks.

Parsons’ Polygon sculpture

The Tyne and Wear Metro, first opened to the public by the Queen in 1980, was the first modern light rail system in the United Kingdom. The Tyne and Wear Passenger Transport Executive (Nexus) commissioned public art through its ‘Art on the Metro’ scheme and continues to do so today. More than thirty artworks have been designed by local communities, as well by internationally-acclaimed artists.

This hexagonal, terracotta-clad sculpture disguises a concrete ventilation shaft for a Metro tunnel deep underground. Its celebrates Newcastle engineer Sir Charles Parsons (1854 to 1931), best known for his development of terrestrial and marine steam turbine engines. The tile designs are abstracted from Parsons’ own engineering drawings.

Sewer vents

Sir Joseph Bazalgette (1819 to 1891), Victorian engineering mastermind and public health visionary, created a vast new sewage system for London in the mid-19th century – 2,000 kilometres of brick tunnels taking raw sewage direct from homes, and 130 kilometres of interconnecting main sewers. As a result, the water-borne disease of cholera, which had taken the lives of tens of thousands of Londoners, was virtually eradicated.

However, the system needed ventilating to prevent a build-up of dangerous gases from the sewers running far below. A network of hundreds of ‘stink pipes’ was erected, in London and across the country, broadly following the line of the main sewers. As high as lamp posts and very easy to miss, the 8 or 9 metre flues dispersed the sewers’ flammable toxic fumes high in the air. The pipes were cast-iron, mostly green, and often decorative with fluting at the base of the column; some were topped by stylised coronets and featured the manufacturer’s name.

Classical-style column

London led the way for the rest of the country in terms of developing sewage systems.  From the mid-19th century onwards, larger town and cities began to construct their own, with the 1875 Public Health Act empowering local authorities to provide clean water supplies and treat sewage before its disposal.

This elegant rooftop-level iron ventilation pipe, designed to resemble a classical column – the ornate arrow pointing south indicating the original line of the sewer – dispersed noxious fumes from Bideford’s sewers below. It is one of four similar ones in the town, probably all made by W Macfarlane & Co, Glasgow, leading Victorian manufacturers of decorative ironwork. The pipes probably date from the re-laying of sewers, around 1901 to 1902.

Sewer Gas Destructor Lamp

Gas destructor lamps, such as the one pictured, also had a role in preventing the build-up of dangerous fetid sewer gas that tended to collect in pockets at sewer high points.

Such lamps were located over these sites, drawing up gases from the underground sewer through a copper tube inside the column, as well as being connected to the town gas supply. The lamps, therefore, both burned off the gases and illuminated the area.

Not what they seem

Greathead Memorial

Old as this statue may seem, it was only erected in 1994.

Following the King’s Cross fire in the underground station in 1987 when thirty-one people died and one hundred were badly injured, London Underground instigated new safety measures across the tube network. Bank station needed an enormous new ventilation shaft, but the proposed site was in front of the City’s historic Royal Exchange.

A radical idea that a statue could double as a ventilation shaft was accepted. Greathead was chosen as an appropriate subject as his pioneering travelling shield for tunnelling was widely used for digging out the tunnels of the underground.

The figure of Greathead was placed on a high plinth, with metal grilles directly beneath the statue linked to the plinth’s vent shaft within.

Duke of Wellington statue

This statue, a few metres from Greathead’s, also has a secret. It has been repurposed as a ventilation shaft, also for the Bank underground station running below. It is now sited on a raised round plinth inset with modern ventilation grilles. 

Written by Nicky Hughes.

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Further reading

From Lamp Posts to Litter Bins: The Stories Behind England’s Street Furniture

Walking on History: Surprising Secrets of Manholes