First time I saw those was in Singapore in 1990 (!). As a fan of public rail, I was really impressed - also, we rode to the terminus back then, and the whole train was empty - looked pretty cool!

Berlin has had them for a few years, as well as Munich.

Having recently been to Paris, what I LOVED about line 1, the "greatest-hits" line, is that the doors open even before the train comes to a complete stop.... So refreshing from the DC metro where it sometimes takes 5-7 seconds (an eternity in that frame of reference) after the train has stopped for the doors to open.

There seems to be a lot of interest in the "snake" trains in Paris. They are called the "Boa" type - which is of course Feench for snake. Here are some photographs of it, in French I am afraid. There are different car connections by different manufacturers - ANF is one, Faiveley is another, titles to the photos. The train type is MF88, this indicates it has been around since 1988. The prototype shown here has now been followed, after some years of tests, by definitive production trains here. You find them on lines 1, 5 and 14. 1 and 14 have rubber tyres, another French difference, whereas 5 has regular railway wheels. 14 has no driver's compartment so you can see forward up the tunnel as well as back down the train. It is also the fastest (and newest) line in Paris.

Athens...
 

No one yet has mentioned the Athens subway system. It was drastically redone and expanded just before the 2004 Olympics, when I visited. The cars were new and shiny and fairly smell-free (especially compared to the NYC subway!) It was easy to navigate, reasonably priced, and operated until early morning (2am maybe?)
My only complaint were that the new marble floors were VERY slippery! I bit it a couple of times! :o

The Metropolitan Line trains are similar in dimension to the District and Circle Line trains (more of a square cross section). I'd watch it wiz by me at Willsden Green every day when I lived in London as I waited for the Jubilee Line.

It is very cool, but what is that smell, which seems to be unique to the Line 14 stations?

There is an article about it in French here.

Basically, it's a sulphorous smell. This is brought about by the nature of the ground under Paris (largely composed of chalk and marls in the parts of town the line goes through, and its position relative to the water table. Remember that a lot of Paris is built on dried marshland (hence 'le Marais'). The extent of this was underestimated at construction time, and works are ongoing to improve the water-tightness of the concrete used, particularly in the stations.

There is a long-standing problem with the smell in the Paris metro in general, thought to be in part due to a type of bacteria found in large quantities in the Paris soil. There have been several experiments with various forms of deodorisation in stations.

Hey thanks! ^ But what took you so long? ;)

-There is also a metro in Lyon, France, which works pretty well; I used it getting to and from the silk district. At the time, it didn't go to the airport, but it does go to the Part Dieu train station, albeit with a transfer for most destinations. The system is cheap and frequent.

-Stockholm also has some deep subway stations, caused, I'd bet, by the fact that the city is on a bunch of islands and the tubes all need to run under multiple waterways.

-Nobody mentioned San Francisco's MUNI Metro subway yet; unlike BART, which it parallels under Market St. for most of downtown, it's really a light rail system which becomes streetcars out in the Sunset and Mission type districts. It constitutes the J-Church, K-Ingleside, L-Taraval, M-Ocean View and N-Judah lines, which share a tunnel from the Ferry Building to Van Ness. The N continues around the waterfront to PacBell Park and the train station in the "Inbound" (sort of) direction. The MUNI system is peculiar, but works pretty well in the metro parts (which are built right on top of the BART, between it and the street), with frequent trains and full interchangability for transferring from the metro to SF Muni buses. I use it a lot.

Probably because tmk, it isn't really a SUBway.

Now that I've been drawn into this thread, I would like to add my vote for DC as being number 1. Aside from the fact that there are some major coverage lapses (I've heard that the residents of Georgetown were partly to blame for this and State of Virginia is still holding out for Metro to pick up the tab on the proposed IAD expansion), it is still my favorite.

For those of you that praised Shanghai's subways, I agree that they are pretty nice, but Peoples Square (where the two existing lines cross; at least 2 more planned) is easily my least favorite subway station on the planet. The walk from line 1 to line 2 is around a quarter mile (shorter in reverse for some reason) and I've been pick-pocketed 3 times there (lifetime total also equals 3).

Sure it is! Have you ridden it? It is underground, in a tunnel that's perhaps 5 miles long, has a system of 5 lines which branch off at either end, and the trains themselves are composed of multiple cars linked together as the trains travel down the tube. It's not until you leave the underground system at either end that the subway train separates into different lines and it becomes the streetcar, which may still be composed of a number of cars linked together as a train. If this doesn't qualify as a "subway", I'm not sure what your definition is.

I wonder if you're confusing it with the "F-Market" line, which is composed of historic streetcars that travel on the surface down Market St., and then go up the Embarcadero to Fisherman's Wharf, or the Cable Cars? THEY aren't subways, for sure. But the Muni Metro Subway even labels itself as one.

Many visitors don't know about it or use it; those of us who live here and work in downtown use it a lot. As a note, they are currently building another line, which will go down the Third St. corridor from near Candlestick Park up across Market St to Chinatown. The line from Pacbell Park to Chinatown is again supposed to be a subway. This is one of Willie Brown's legacies.

I just would like to suggest everybody the great FREE software METRO! it's a worldwide subway map available for Palm, pocketc pc and some mobiles. It's a must have!

Such a system is known to transit professionals as a "Pre-Metro", as opposed to a true metro/subway. The pioneers of the approach were in Germany, particularly Frankfurt and Cologne.