Park Avenue seems to have an uncanny ability to become a sweltering strip of molten asphalt in the middle of Summer. The double-wide street allows for more sunlight to peek through the buildings, and even though a great number of trees do their best to make up for it, you can still find yourself slowly melting into the relentless traffic.
The alternate side effect of this openness is the fleeting views you can get of many buildings and landmarks. Sure, some will enjoy the long stretch of (unworkable) parkland in the middle of the road, but I get more joy out of momentarily seeing the Chanin, or Empire State Buildings. It's a little bit of a surprise on a street where the expected view is generally just the MetLife building.