Buenos Aires Underground. The interesting thing is that the subway cars have front windows for your enjoyment.
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/29638083@N00">Luis Argerich</a> from Buenos Aires, Argentina
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/lrargerich/3121044070/">Train after the curve</a>