Plan your trip of well-known spots that worth visiting and take subway to these spots. Last June, it takes me one day to cover famous locations. I planned my trip for months. A smartphone with Moovit and citymapper app is my friend and i was quite satisfed with my journey
I have no idea about Harford City, but it may be easier to take the subway into NYC and purchase a hopper vus ticket which takes you all around. It takes more than one day to take in everything.
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