Please visit Manhattan's best kept secret - the Jefferson Market Garden :-) It's a small but peaceful and exceedingly attractive garden with roses, birdbaths, stone benches, a gold fish pond and other exotic flowering plants.

http://www.jeffersonmarketgarden.org/

Hours: open afternoons, except Mondays from May to October.

The garden is on Greenwich Avenue between Sixth Avenue and West 10th Street in the midst of Greenwich Village, right behind the Jefferson Library. I think the City Sights bus travels down Fifth Avenue. When you get on board, ask the driver for directions to Sixth Avenue and Greenwich Avenue. The Jefferson Market Library building is a stunning red brick structure with Gothic details, it is easily spotted. Just in case, here's a picture in the follwoing link:

http://en.wikipedia.org/wiki/Jefferson_Market_Library

Enjoy your trip (to NYC and, hopefully, to the Jefferson Market Garden)!

http://www.centralpark.com/pages/attractions/conservatory-garden.html

If you happen to be in the East Village, Tompkins Square Park is nice, and there's a cute little community garden very nearby on Avenue B between 5th and 6th Streets. Not worth a special trip but a nice spot for a little sit-down if you're in the area.