I recommend "Brooklyn Bridge" and "Brooklyn Heights Promenade".
Brooklyn Bridge is nice walk distance and there is crowed in many tourist. It's very interesting and fun!
Brooklyn Heights Promenade is known as sercret spot! We can see BEAUTIFUL sight of Manhattan from there. Sunset is BEST!!!
If you're interested in both of place, you can take a subway from the city. Take a green line and get off at "Brooklyn Bridge". Then you can see the Bridge!
The nearest station of Brooklyn Heights Promenade is Red line "Clark st".
If you haven't been there, you'd better to visit there!