Good views of Grand Central Terminal, and possibly a great photo opp if you're visiting.
Note that on the ground in the sidewalks of 41st Street, both sides, are library plaques you may want to take a look at, and on Park Avenue there are similar plaques about the buildings in the area.
Cache shouldn't be too hard to find but the area is super crowded during the day so just something to keep in mind.
Also note that for the pedantic among us it's Grand Central Terminal. Terminals are where trains end, whereas stations are where trains stop and then keep going. So there's actually no such place at Grand Central Station, although many do call it that.
Note that you'll need your own pen to sign the log.