Walk up to Riverside Park until you hit 181st street. Sit under the Little Red Lighthouse and enjoy one of the best views in the city, imo.

Rarely do people go there. I spent many'a afternoons there with my late dog. The only noise is the muffled noise of the GW Bridge above you, and maybe the occasional boats passing by.

Obligatory post with a pic I made suggesting this on r/nyc a few years back