Population by administrative area is irrelevant.

"Comparing urban areas in the European Union, Eurostat, the statistical agency of the EU, places Paris (6.5 million people) second behind London (8 million) and ahead of Berlin (3.5 million), based on the 2012 populations of what Eurostat calls "urban audit core cities"." — Wikipedia.

Exactly. The City of London is administratively a city and a county. Looking at these boundaries, it is the smallest English city [1].

[1]: https://en.wikipedia.org/wiki/City_of_London#Geography

That's somewhat different, though. The City of London is not London, the capital city of the UK. The latter is formally Greater London, consisting of 32 London Boroughs and the City of London. The two are different administrative entities entirely, with City of London e.g. having its own Lord Mayor separate from the Mayor of London, and with the ceremonial country of Greater London explicitly excluding City of London.

Nested administrative boundaries is a UK speciality (e.g. England, Wales and Scotland are countries within a country).

The 'City of London' is a quirk it is actually a very small borough within the city of Greater London, which has a population of something like 8 million and is very roughly up to zone 6 on a tube map. For the regional population I vaguely remember a statistic that there are 20 million people within 30 miles of trafalgar square, but I can't back this up right now.

That City (big C, the administrative area) is indeed tiny, population 8,000, and is distinct from the geographical city of London (small c) population 8,000,000.

And, notably, predates the English monarchy and technically exists somewhat separate from the UK...

You will notice that you have left Berlin by all the trees and fields around you. You will notice leaving Paris by the huge motorway you have to cross before you enter the surrounding urban districts.

And Boston has only 600k inhabitants, right?

(4M if we count the Metro area)

Most of Boston seems doable for car-free too, but I don't know if the public transportation can handle it. It's already taxed at rush hour and other peak times. I can't imagine everybody could get to work on time if everybody had to use it without major skewing of some schedules.

It seems like a strong telecommuting infrastructure and culture should be a part of this.

Public transit in Boston is already choked at rush hour, and badly in need of repairs (including complete fleet replacements for two subway lines, now scheduled to start in a couple of years) -- witness the total breakdowns last winter, which had some lines out of service for weeks.

And witness the repercussions. On the third day of the crisis, the Red and Orange lines were out, and a lot of people who normally came on them, drove instead. The result was that Cambridge was utterly crippled with traffic. On my way back from Kendall to Medford, I walked, and I got home earlier than anyone I know.

Right! And DC has only 658,893 inhabitants. Let's ignore its metro area of 4.5 million and CSA of 9 million.