Tucked in the extreme south east corner of the Battery Roof-top Garden is the Secret Garden, a refuge separated from the rest of the garden, with a cozy bench for two, oriented to the view over Battery Park and Brooklyn to the Atlantic. The secret garden features rough stone paving, boulders, and an array of alpines rarely attempted on a green roof.
Plants in the Secret Garden include Opuntia humifusa (“Prickley Pear” Cactus), native to New York State, but not seen in lower Manhattan for, I would guess, about 400 years:
Battery Rooftop Garden Blog 
I must say that the view is breathtaking, both off the ledge and inside this wonderful garden. A restful zen experence for the owner and guests alike.
Mr. Tanaka