|This is New York - Underground|
Not just the subways, although that's a gimme. But how many buildings connect to the subways, how many barber shops, pizza joints, newsstands, shoe shines, gourmet delis and fitness spas are under people's feet. And not just dirty Penn Station shops either. Most of the hotels in the Shmancy class (and all of the hotels in the next bracket, the Fancy-Shmancy) have their spas, orchid shops, and bespoke hair stylists down there.
Would it be possible to walk underground from Washington Heights to Wall Street without using the subway?