What is the first city that comes to mind when I say "Greatest City in Europe"?

My first thought was “London. No, wait, Paris is more European, so Paris.”

Heidelberg. Don’t ask me why, I don’t know.

(Without reading the spoilers or anyone else’s responses)

Paris

I spent a week there last summer so I thought Paris.

But I liked Rome better. And Venice even more than that. I’d spend a month in Venice if I had the time and money.

I would love to see London but alas the exchange rate makes that incredibly difficult right now.

Paris.

My thoughts before reading the spoilers:
"Hmm… does he mean Paris or Rome?
"Barcelona? No, that’s just my bias; even Spaniards think Madrid is at least as ‘great’.
"What about London? If Britain is included, then London’s probably third, I guess, but it can’t really compare to Rome or Paris culturally. "

Them’s fighting words! In what way does London not compare to Paris or Rome culturally?

Paris. London is in the running, but too much of it wall to wall McDonalds for my tastes.

My response, before reading the spoilers (or any of the other replies):

Paris is what most people would probably say is the “greatest city in Europe.” I don’t know whether they’re right or not—I suspect Paris may be overrated. London may well be a greater city, but it’s not as quintessentially European, as England is not as “European” a country as France is, being off on an island rather than part of the continent. (And, from an American perspective, not being as foreign, since they speak English there.)

In my experience, Barcelona seems to speak to people in a way that Madrid does not.

I like Madrid, it’s a fine city with some amazing museums and a copious amount of high end shopping and dining opportunities.

That said, Barcelona is truly, hauntingly sublime, and has an indefinable magic that Madrid can only dream of…

Well, there are only two Alpha++ Global World Cities (London and New York), so it’s hard to imagine an answer other than London.

It’s also the top world financial center (with NY being #2). “According to the WEF (World Economic Forum) London in the United Kingdom has now replaced Wall Street as the centre of the financial world” (from that link).

It’s the top Worldwide center of Commercial Index (again, NY is #2) [same link as above].

It’s the largest urban area in the whole of Europe, has the largest city GDP in Europe, Heathrow is the busiest airport in the world (by # of international passengers, plus London has the busiest airspace on the planet), the London Underground is the most extensive underground railway network in the world, the West End is the world’s biggest theatre district (narrowly beating out Broadway).

New York Magazine calls London “the global capital of the 21st century.”

A 2009 report (commisisoned by The Independent) names London “the capital city of the world”, followed by New York. There is some dispute over those top two positions, but whichever way round they are London beats any other European city.

I can see arguments for Paris, but my vote goes to London. It’s a global powerhouse in so many arenas. It’s only rival in the world is New York City.

I think that people underestimate the sheer clout of London.