This is a great park, from free concerts to summer to the Brooklyn flea markets over the weekend or take the ferry across the river. Rain or shine I never get sick of that view.
Moma is worth a visit, but for a more lively Art experience ánd for free, one should visit Chelsea. A colony of 400 Art Galleries, showing the best in contemporary art. Running straight through is the high line, a 1 mile long linear park, build on a former railroad-spur, worth the walk.
After the full moon, when the tide is the lowest, you'll find a century of fossils from a gone NY, trails of washed-out rainbow colored bottles, a graffitied shipwreck buried by time. Hundreds of years of history written in the sand.
The different views of the skyline are unbelievable. I especially like rooftop views from different apartment buildings. Try to get on top of an apartment building. This is the view from my apartment...