The City Beneath the City

The most revealing view of a city is occasionally available through a hole surrounded by temporary fencing. Above ground, everything appears reasonably settled. There is a pavement, a coffee shop and a building whose developer describes it as timeless. Below, several generations of pipework are attempting to occupy the same space without causing an incident.

We tend to imagine cities horizontally, as arrangements of streets and destinations. Their more interesting dimension is often vertical. Beneath the visible city sits an accumulation of waterways, tunnels, cables and decisions made by people who could not have anticipated what we would eventually try to put on top.

A city is difficult to redesign partly because so much of the previous design is still working.

The river has not left

London’s Fleet is often described as a lost river, which makes its disappearance sound like an unfortunate clerical error. According to London Museum’s history, it flowed from Hampstead and Highgate towards Blackfriars, supporting centuries of urban life and industry before pollution and development transformed its role.

As the city grew, the Fleet became an open sewer. Sections were progressively covered. The watercourse was incorporated into the machinery of the city and removed from ordinary view.

This was not simply a failure to appreciate picturesque scenery. A polluted urban river presented practical problems. Covering it made sense to people confronting conditions rather less attractive than the phrase “riverside location” now suggests.

But disappearance from view is not disappearance from the system. Water still needs somewhere to go. The city can change the channel, conceal it and rename its function. Gravity remains unimpressed by the branding exercise.

There is something instructive about a place whose geography survives as plumbing. What looks like a purely human arrangement is still negotiating with the landscape underneath.

Progress does not always mean adding something

Manchester offers a different turn in the story. At Mayfield, part of the River Medlock was uncovered and made central to a new park. Manchester City Council describes the project as bringing a previously concealed stretch back into daylight.

The sequence is pleasingly awkward for a simple account of progress. One generation encloses a river to accommodate its idea of a useful city. Another spends money exposing it to accommodate a different one.

Neither decision can be judged sensibly without its circumstances. The earlier city had industrial pressures and priorities. The later one wants public space and a different relationship with water. What changes is not merely the engineering, but the answer to what the place is for.

Sometimes improvement means removing an earlier improvement. This is difficult to fit into the usual development photograph, where the important person is expected to stand beside something newly constructed rather than a successful absence.

The neighbourhood below the pavement

The underground city is not composed entirely of atmospheric relics. Much of it is contemporary, necessary and inconveniently close to something else.

A 2022 government update on the National Underground Asset Register put the UK’s buried network of pipes, cables and sewers at around four million kilometres. That was a national estimate, not a measurement of one city’s tangled underside. It nevertheless gives some sense of how much infrastructure operates beyond ordinary inspection.

The register’s purpose is to make information about underground assets easier to access together. Its published guidance also makes an important distinction: better records do not replace ground investigation and safe digging.

That caveat contains a useful lesson about knowledge. A line on a screen is information about a physical object. It is not the object, and the confidence with which the line is drawn does not make a buried cable move to match it.

The person investigating a street therefore has two problems. They must understand what is there and establish how much to trust what they have been told. Excavation is, among other things, an unusually consequential form of fact-checking.

A railway that outlived its reason

London’s underground postal railway makes the historical layers particularly tangible. Opened in 1927, Mail Rail carried post beneath the city until its service ended in 2003. Its tunnels now form part of The Postal Museum’s visitor experience.

The original proposition was practical: move mail beneath congestion rather than repeatedly negotiate it at street level. The railway was built around the geography and operating needs of a particular postal system.

A tunnel, however, is a durable commitment. The organisation above it can change its processes and locations much more readily than the tunnel can follow. Infrastructure may remain physically impressive after the arrangement that justified it has altered.

This is why the abandoned underground is so compelling. It records futures that once seemed permanent. Somebody invested considerable intelligence and effort in making a system work, and for a period it did.

There is no need to treat its later retirement as proof that the original decision was foolish. Longevity and usefulness are related, but they are not the same thing. A railway can have a successful working life without being owed eternal employment.

You cannot close London for refurbishment

Other systems remain indispensable precisely because they cannot be retired. London’s Victorian sewer network is an example of infrastructure whose continuing usefulness creates the setting for its own alteration.

In February 2025, Tideway announced the final connection of its new tunnel to the existing network. The 25-kilometre tunnel joins the Lee Tunnel as part of a larger wastewater system. The new work operates through connections to what was already there.

The project company’s announcement establishes that milestone; it is not an independent verdict on every promised environmental outcome. The engineering relationship is the point here. Modernisation involved extending a working system, not announcing that the old version would cease to exist on Monday.

Anyone who maintains software will recognise the difficulty. Existing users persist in needing the service while the people responsible attempt to improve it. In a city, the users also insist on flushing.

This does not make change impossible. It makes knowledge of the existing arrangement valuable. The supposedly unglamorous person who knows where something connects may be more useful than the person with the most comprehensive vision of starting again.

What deserves to survive?

It would be easy to turn all this into an argument for preserving everything. But old infrastructure can be inadequate, dangerous or simply no longer worth maintaining. Age establishes historical interest, not an automatic entitlement to a repair budget.

The harder judgement concerns what an inherited system still enables, what it obstructs and what would happen if it were removed. The answer may be preservation, replacement or a new connection. At Mayfield, it included taking the lid off.

The underground city encourages a more patient understanding of change. Its layers show that earlier decisions are neither wholly disposable nor permanently binding. They become conditions with which the next decision must contend.

That is why a hole in the road deserves more than irritation, even if irritation is a reasonable response to the diversion. For a moment, the city exposes the practical negotiations that make its confident surface possible.

Above ground, an advertisement promises a completely new way of living. Beneath it, somebody is establishing which of three pipes is still live. The new way of living will have to wait until they are sure.