Places in London to visit to kill some time?

Hi everyone,

Long story short, I'm going into London & I'll have some time to kill before an event before an event in the late afternoon. Can be any length between 1-4 hours.

Looking to visit some areas with nice views / peaceful / or just any other leisurely area (as I don't come here often and would like to see more of London).

Would love to hear all your recommendations (and yes, I have been advised to visit Greenwich park).

Thanks!