Sorry, folks. I hate to tell you that you are all wrong, but when I don't even see Moscow on the first page, I need to set things right. Moscow has the best metro system in the world. First of all, let's forget the fact that Moscow has absolutely THE MOST BEAUTIFUL stations in the world. They are like works of art, with statues, mosaics, artwork, marble, bronzes. Feel free to google a few of my faves--Novoslobodskaya, Mayakovskaya, Komsomolskaya. No let's forget that--let's talk about efficiency. Did I mention the trains run every 90 seconds? Yeah, that's right. You don't need to go running at breakneck speed to catch your train--there is literally one behind it in 90 seconds. Wherever you go in Moscow, you are usually only 2 blocks away from a metro station. And the crossings from adjoining stations are underground, so you needn't come all the way up and buy another ticket. No, you can travel around on the one ticket. Also, they are clean--an army of cleaners work to keep them spotless, and another army of metro police keep them safe. So my vote goes to Moscow.