What a truly amazing and interesting place. Hamilton Bridge Skatepark is situated smack dab in the middle of the Alexander Hamilton Bridge and the Washington Bridge (not the George Washington Bridge, that's different). On the East it is bordered by the busy Harlem River Dr and on the West a small hill that opens up to the onramps of the nearby bridges. It's a busy, urban setting that screams NYC at every angle.
The skatepark is normally busy with skaters, but if you go around opening time on a weekday like I did, you'll catch the park empty with the surrounding walkways and stairs inhabited by the occasional homeless camp. In some ways, it feels like the city spent a lot of money to revitalize the place a few years back, building this enormous skatepark, and then basically just said "Ok, we did our part so see ya!". What I mean by that is that the park is, in a word, broken. Lampposts are taken out of the ground, bulbs are smashed, garbage is strewn everywhere, and graffiti is more or less the decoration for any concrete and brick surface. If you walk downwards from the top of the hill where the skatepark sits, you'll be greeted with broken sidewalks, overgrown weeds, and an odd open roadway that leads right to the heart of the Harlem River Drive. It's an odd place and I love it. You get to walk underneath the Amsterdam Ave. and Trans-Manhattan Expressway and totally feel like you've been transported to another city altogether. Nobody to bother you. To me, it's a good escape from the busy-ness that is just a few hundred feet uphill.
Check it out by heading to the 181st Street Subway on the 1 line and walking to the skatepark entrance at 181st Street and Amsterdam Ave. (Pro-tip: Don't follow the usual Google Maps directions to this place, it's very wrong).