NYC Subway Ranks 7th Worldwide

The mere fact that NYC's subway is the only one that runs 24 hours seems to be a slam-dunk reason to rank it #1. NYC's subway is also very cheap compared to London's. However the travel site is based in the UK, so there may be some bias at hand. Check out the ranking on Virgin-Vacations.com, there are some great photos of the various systems. What's your favorite subway in the world?