Brooklyn Bridge
Brooklyn Heights Promenade
Staten Island Ferry
Gantry Plaza State Park
Governor’s Island
Roosevelt Island
All free except the last one because you have to take a cable car, but it is only a couple of dollars I believe.
Good luck!
Enjoy
There are a number of boat cruises around Manhattan that you can get comp tickets for. They make their money off of alcohol sales but you don’t have to buy anything and the views are spectacular. Check out the Goldstar app for reservations.