There are several things about this bike that caught my attention.
At first glance this Schwinn near Columbia University looks like its owner might be right back. The bike is upright and looks like it is ready to be ridden. Take a closer look and you'll see that the bike has several tell-tale signs of being abandoned. Note the flat tires, droopy chain, and bare metal seat.
Something curious: the bike has two locks. The u-lock attaches the front wheel to the frame, and the chain lock attaches the frame and rear wheel to the sign post. This is a bike whose owner cared about it enough to not have it stolen! Why, then, was it abandoned?
So far, the vast majority of abandoned bicycles I've found and photographed have been Huffy, Schwinn, or Peugeot brands.