Underneath the big Apple now, since those steam tube make it a temptation. It is not like the metro in Paris. It is more "technical"… more pragmatic maybe. It seems rough. The efficiency is there and there is a little bit of decoration on the walls of the stations. And it has not changed for ages. That's what I like about this city : layers of time with no desire to hide the past. Same for the architecture in the streets, where you find the most modern constructions in between some remnants of the old life. This is the charm of New York. They keep their traditions. If things are efficient, no need to change them or camouflage them with a coat of modernity, like you can find in Paris. To go back down in the subway the big difference with the Paris metro is the noise level, which borders on the unbearable. But one positive thing : it works all night, where public transportation disappears in Paris around 1 AM.