Manhole covers as markers of history, society — and space travel?

As a child I used to suffer from a recurring dream. I would be walking down a familiar stretch of road in London when I somehow fell through a hole in the pavement. Although it didn’t seem to be particularly deep, it was dark down there and no one could hear me. I’m now not entirely sure if it was a manhole or one of those wooden trapdoors where beer is delivered to pub cellars but the memory has stayed with me and, although I’m not afraid of falling down a hole, there is a residual strange draw to the idea that there is an alternative, parallel city beneath the pavements. And that the cast-iron plates covering them are the doors to that underworld.

The Romans had manholes of course (they were obsessed with sewers), and they were surprisingly similar to our own. There is one in the Römermuseum in Vienna, chiselled from stone. It is rectangular and decorated with four almond-shaped openings to allow a tool to gain purchase and lift them up.

Our streets are full of holes — for pipes and cabling, for rainwater drainage, water hydrants for standpipes and so on, but perhaps the most interesting and varied are the myriad coal-hole covers in the paving in front of houses which once opened for the delivery of coal directly into cellars. They are most likely to be made of cast-iron and to date from the second half of the 19th century.

These manhole and coal-hole covers are, it turns out, a bit of a cult. UK Labour party leader Jeremy Corbyn is a fan, frequently snapping coal plates on his mobile (“people think it’s a little odd”, he admits). The odd hobby, however, is nothing new. In 1869, at the height of coal-plates’ popularity, a medical student named Shephard Taylor sketched dozens of designs he found on his walks and later published them in his book Opercula, using the medical pseudonym Aesculapius Junior. Taylor coined the phrase which had been a biological term (a cover, for instance, for the gills of a fish).

My friend Christian Küsters, a London-based graphic designer, has turned coal-hole designs into a series of prints and even T-shirts — there’s something so strikingly graphic about their form that they lend themselves to everything from Tumblr, Twitter, Facebook and Instagram sites to beer mats. Look up #Opercula on Twitter. I particularly like Christopher Howse’s account (@BeardyHowse).

The internet is surprisingly well-stocked with manhole covers; perhaps their pure graphic form suits the medium, perhaps the internet is just stuffed full of nerds. The idea of manholes as medium, however, is nothing new. In 1962 the art dealer, poet and curator Victor Musgrave put on a display of cast-iron manhole covers in his Soho gallery.

These iron covers also act as markers, as labels or badges for streets, which tell us huge amounts about the history of industry and development, about urban terroir and locale. The names of their manufacturers are cast into their surfaces so that the lettering becomes an anti-slip surface; the text becomes functional. The history of the city is there to see, inscribed in these iron covers. In London, for instance, you might find covers embossed with the name of George Jennings, the unitary engineer who introduced the flush toilet to London at the Great Exhibition of 1851, an invention which quickly became so popular that the city’s decrepit sewer system was unable to cope and the contents were flushed into the Thames, leading to the Great Stink summer of 1858. You might find others featuring the name of the self-promoting sanitary engineer Thomas Crapper, often with perforations to allow the escape of gas from sewers and avoid a build-up of pressure and the ultimate explosion which might propel a chunk of iron through the city at ferocious speeds.

Which does, in fact, happen more frequently than you might expect — there was a spate of flying manholes in New York only last year. You might then be surprised to see that some of the London covers were made in Chelsea, once a place of heavy industry. You might see coal-hole covers studded with small roundels of thick glass to bring a little light to the cellars below the pavements, or others with concentric rings or complex webs of piercings — the variety of patterns is breathtaking. Sometimes you see the ghosts of technologies long-gone, manhole covers marked with the names of telegraph or tramway companies, municipal gasworks or electric light companies.

In Tokyo you might find manhole covers in garish colours, ornamented with the vividness of cloisonné. They portray samurai, swirling carp, Mount Fuji or wide-eyed kitsch Manga characters. Rival municipalities compete to install the most beautiful and Instagramable examples.

In New York the selection is more limited and literal, many just reading “NYC Sewer” but I do like the ones that are embossed with “DANGER” in caps without explaining quite what is so dangerous about them.

In Seattle they have covers embossed with the city street plan. In some cities you might find a manhole cover with the remains of a street surface that has disappeared elsewhere. I have seen timber leftovers from the days when roads were lined with wood to damp down the noise of iron carriage wheels trundling along them. Others may be concreted in, painted over, graffitied on or have fossils or stones inlaid in them.

Manhole covers are, in a way, a kind of street jewellery, little moments of craft in the endless grey membrane of asphalt and granite. Yet perhaps more intriguingly, they are portals, openings to an underworld which we only partly comprehend. They retain a touch of mystery, wormholes connecting the private and public realms, between pavement and property and between the worlds of light and dark.

Unexpectedly, a manhole cover was also, possibly, the first spacecraft. In an apocryphal, but still enjoyable story, Dr Robert Brownlee revealed that during the Operation Plumbbob nuclear tests in Nevada in 1957, a metal manhole cover over an underground explosion was expelled with such force that it would have quickly reached the earth’s escape velocity and was blasted into outer space a few months before the Soviets launched the Sputnik. It was never found.

Incidentally, one of the questions frequently asked of applicants for jobs in Silicon Valley used to revolve around manhole covers. Why are they round?* If I had known the answer, perhaps I’d never have had that nightmare.

* Because that way they can’t fall in the hole, whereas a square or rectangular cover, if slightly at an angle, could do so

Edwin Heathcote is the FT’s architecture and design critic

Photographs: JTB Photo/UIG/REX/Shutterstock; Jon Arnold/AWL Images/Getty Images; Rene Burri/Magnum Photos; Richard Leandry/Getty Images