Which is the largest city in Europe?

Nobody tell Marine, Geert, Donald and the lads about this, honestly, they'll go mad. Image: Julian Nitzsche

It's London, right?

It’s the big one, the leviathan, the great leader and global bastion – standing streaks ahead of its tiddly continental competitors, head and shoulders above those EU capitals and provincial cities across the Channel. Surely, undeniably, inevitably, London must the largest city in Europe.

Right?

Well, so as to avoid the imminent danger of sounding like a Brexit-sponsored advertising campaign, the answer is: yes and no.

There are two obvious variables here – how do we define Europe, and how do we define a city?

First, the likely less contentious of the two options – how do we define Europe’s cities?

Within the city walls

To start with, there’s an obvious option: how the cities define themselves. In terms of the administrative limits of each city, a hierarchy becomes clear – and yes, London is on top.

Mmmmm, London. Image: 0x010C.

To avoid getting bogged down in the detail of each individual census, national statistics office, or city population office, here’s the listing of cities by population within city limits.

1. London, UK: 8,673,713

2. Berlin, Germany: 3,670,999

3. Madrid, Spain: 3,131,991

4. Rome, Italy: 2,870,336

5. Paris, France: 2,224,000

6. Bucharest, Romania: 2,106,144

7. Vienna, Austria: 1,657,960

8. Hamburg, Germany: 1,787,408

9. Budapest, Hungary: 1,759,407

10. Warsaw, Poland: 1,748,916

But wait, what?

London realistically has a lot more than 8.6m people, and there are definitely bigger urban areas in Europe than Berlin, with a measly 3.6m.

And what's happened to Paris? Why would everyone be so obsessed with a city of just 2.2m people?

Something’s up.


If you broaden the net, and start talking about ‘urban agglomerations’ – basically, cities and the bits around them that also function as part of the city – we get a very different picture.

Near the city walls

There are all sorts of caveats and rules that go into these measurements, from the United Nations’ Department of Economic and Social Affairs, which published its population estimates for 2015 in its World Urbanisation Prospects tome.

The core idea is that, discounting rivers, parks, roads, and industrial fields, urban agglomerations are built-up areas where houses are not more than 200 metres apart. But the definition doesn’t stretch as far as satellite cities: so London’s commuter belt, with its stretches of evil greenbelt as a dividing line, don’t count, but the Parisian suburbs, very much close to and part of Paris proper, do.

And the results on this measure are, obviously, rather different:

1. Paris, France: 10,843,285

2. London, UK: 10,313,307

3. Madrid, Spain: 6,229,254

4. Berlin, Germany: 6,000,000

5. Barcelona, Spain: 5,258,319

6. Rome, Italy: 3,717,956

7. Milan, Italy: 3,098,974

8. Athens, Greece: 3,051,899

9. Lisbon, Portugal: 2,884,297

10. Manchester, UK: 2,645,598

There’s a variant version of this definition, too: one which includes areas that are generally built-up but aren’t specifically centred on one particular city. Demographia’s figures are produced on that basis, and that comes up with a similar picture, but with a very different front-runner:

1. Ruhr Area, Germany: 11,100,000

2. Paris, France: 10,858,000

3. London, UK: 10,236,000

4. Berlin, Germany: 6,269,000

5. Madrid, Spain: 6,171,000

Düsseldorf, the heart of the Ruhr Area. Image: Cristian Bortes.

To avoid list fatigue, let’s just say that the rest of the top ten runs in roughly the same way.

Emotionally attached the city walls

But to everyone who grew up sort of near a big place but not really in the big place, and got sick of explaining to visiting Americans exactly what and where Hemel Hempstead was, there’s another handy definition that produces a picture of the metropolitan area, or functional urban region. That is to say; the area where realistically you’re part of the family of the urban centre, in terms of living, commuting, and functioning, even if you’re not technically part of it.

These figures from Eurostat, the statistics arm of the European Union, offer that view:

1. London area, UK: 14,031,830

2. Paris area, France: 12,005,077

3. Madrid area, Spain: 6,378,297

4. Barcelona area, Spain: 5,445,616

5. Ruhr area, Germany: 5,045,784

6. Berlin, Germany: 5,005,216

7. Milan area, Italy: 4,267,946

8. Athens, Greece: 3,863,763

9. Rome area, Italy: 3,700,000

10. Warsaw area, Poland: 3,304,641

So, that's sorted, right? It's London, or Paris, or possibly the Ruhr. We cool?

Except, no. Because Europe itself isn’t that simple, as we’re about to find out.

Whose Europe is it anyway?

There’s the EU, the Schengen Area, the Customs Union, the EEA, the Continent, and then the sticky issue of Europe itself.

Does it stop at the Bulgarian and Greek border with Turkey? The rickety border Russia shares with Ukraine, Belarus, Latvia, Estonia, and Finland?

Does Europe end at the Bosporus, the ancient meeting point of East and West at Constantinople and Byzantium at the entrance to the Black Sea? Is Istanbul in Europe, or only the part of it on the right side of the water?

So, let's include European Turkey, give Istanbul the benefit of the doubt, and stretch Europe as far as the Ural mountains in Russia. And then, the size rankings change again:

By city limits (the first definition), here’s how things look:

1. Istanbul, Turkey: 14,804,116

2. Moscow, Russia: 12,330,126

3. London, UK: 8,673,713

4. St. Petersburg, Russia: 5,225,690

5. Berlin, Germany: 3,562,166

But as before, that definition of the city isn’t particularly useful – as it shunts the Continental giant of Paris to the relegation zone purely because the administrative area of the arrondissements is tiny.

With so many fluctuating figures based on so many different definitions, it’s probably more useful to conclude by dividing European cities into three broad classes. Let's call them megacities, very big cities, and quite big cities.

In the megacity category, we get roughly:

1. Moscow, Russia: 17.9m

2. Istanbul, Turkey: 14.8m

3. London, UK: 14m

4. Paris, France: 12m

5. Ruhr Area, Germany: 11.1m

Moscow, much bigger and shinier than you thought. Image: Dmitry Mottl.

The very big cities follow:

6. Madrid, Spain: 6.4m

7. Barcelona, Spain: 5.5m

8. Berlin, Germany: 5m

9. St Petersburg, Russia: 4.8m  

10. Milan, Italy: 4.2m

And then the rest. Rome, Athens, Warsaw, Lisbon, Manchester, Bucharest, Vienna, and so on, happily muddling along somewhere between 2m and 4m people.

The more you know.

Bonus point

If your city obsession is beyond entry level, a brief lesson in megalopolises (megalopoles?). Popularised in the early 20th century, the term applies to a chain of cities that are sort of near each other and can be thought of as working in a roughly coherent whole – the typical example being the north-eastern seaboard of the US, with its smudge of Boston, New York, Philadelphia, Baltimore, and Washington, D.C.

In Europe, for some reason, this has become a battle of the bananas.

The ‘Green Banana’ comes in third place, with roughly 40m people spread between the cities of Gdansk, Warsaw, and Katowice in Poland; Ostrava, Prague, Olomouc, and Brno in the Czech Republic; Vienna in Austria; Bratislava and Zilina in Slovakia; Budapest and Gyor in Hungary; Ljubljana in Slovenia; Zagreb in Croatia; and Trieste in Italy.

In second place we have the Golden Banana, with 45m or so. The colour comes, in theory, from the luscious sands of the Western Mediterranean, with the megalopolis defined as including Turin and Genoa in Italy; Lyon, Nice, Toulon, Marseille, Nîmes, Montpellier, Narbonne, Perpignan, and Toulouse in France; Monaco in Monaco (obviously); Andorra la Vella in Andorra; and Manresa, Girona, Vic, Barcelona, Tarragona, Catellón de la Plana, Sagunt, Valencia, Alicante, Murcia, and Cartagena in Spain.

But supreme among European transnational megalopolises comes the mighty Blue Banana. This mythological elision of cities harbours 130m people and includes (deep breath in) Liverpool, Manchester, Leeds, Sheffield, Birmingham, and London in the UK; Brussels and Antwerp in Belgium; Amsterdam, Rotterdam, The Hague and Utrecht in the Netherlands; Luxembourg in Luxembourg; Cologne, Düsseldorf, Dortmund, Essen, Duisburg, Wuppertal, Frankfurt, Munich, Stuttgart, and Nuremberg in Germany; Strasbourg and Lille in France; Zürich and Basel in Switzerland; and Turin, Milan, and Genoa in Italy.

So yeah. There’s that. 

Jack May is a regular contributor to CityMetric and tweets as @JackO_May.

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How bad is the air pollution on the average subway network?

The New York Subway. Image: Getty.

Four more major Indian cities will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building its 14th subway line, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line after waiting for almost 100 years for it to arrive.

In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than 120m people commute by them every day. We count around 4.8m riders per day in London, 5.3m in Paris, 6.8m in Tokyo, 9.7m in Moscow and 10m in Beijing.

Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, half of the world’s population is now urban. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.

Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO2), produced in part by industrial emissions and road traffic, are responsible for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.

But what is the air like that we breathe underground, on the rail platforms and inside trains?

Mixed air quality

Over the last decade, several pioneering studies have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.

Subway, Tokyo, 2016. Image: Mildiou/Flickr/creative commons.

For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in Barcelona, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in Hong Kong, Mexico City, Istanbul and Santiago de Chile.

Of wheels and brakes

Such differences have been attributed to different wheel materials and braking mechanisms, as well as to variations in ventilation and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.

Second Avenue Subway in the making, New York, 2013. Image: MTA Capital Construction/Rehema Trimiew/Wikimedia Commons.

Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.

In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.


To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. New York subway workers have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the Stockholm subway system.

But a note of caution is struck by the observations of scholars who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.

The dominantly ferrous particles are mixed with particles from a range of other sources, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.

Comparing platforms

The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of IMPROVE LIFE project with additional support from the AXA Research Fund.

It reveals substantial variations in particle-matter concentrations. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of air-conditioning has been shown to produce lower particle-matter concentrations inside carriages.

In trains where it is possible to open the windows, such as in Athens, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at high speed.

According to their construction material, you may breath different kind of particles on various platforms worldwide. Image: London Tube/Wikimedia Commons.

Monitoring stations

Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the Barcelona subway system, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.

To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.

The ConversationSuch research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.

Fulvio Amato is a tenured scientist at the Spanish National Research CouncilTeresa Moreno is a tenured scientist at the Institute of Environmental Assessment and Water Research (IDAEA), Spanish Scientific Research Council CSIC.

This article was originally published on The Conversation. Read the original article.