At the end (or the beginning, depending on what direction you are heading) of 34th Street is the East River. This river runs between the island of Manhattan and Brooklyn and Queens, which are on the far West edge of Long Island.
The East River isn’t actually a river, but a salt water tidal estuary. Since that is a lot to say, we call it the East River. It connects Upper New York Bay on its south end to Long Island Sound on its north end. The river is about 16 miles (26 km) long and and 600–4,000 feet (200–1200 metres) wide. The width has changed over the last 300+ years of shipping coming into the East Side of Manhattan and Brooklyn and Queens.
The river was once a major thoroughfare for shipping. Ships sailed into the slips in lower Manhattan in the 1600 and 1700s. Ferries crossed the river starting in 1814, making Brooklyn accessible for workers and helped change Brooklyn to a residential area instead of farms. The Brooklyn Navy Yards opened in 1801 and the docks in Red Hook and DUMBO constantly had ship traffic coming in starting in the late 1700s. The docks in Brooklyn saw many sailors leave the US to go fight in wars.
The slips and docks are all gone and replaced by parks. Along the Manhattan edge of the river is East River Greenway (Esplanade) in this area. This is a 9.44-mile-long (15.19 km) pathway for walking, running, and biking. Great views of the river and Queens are visible in the 34th street area. Just walk to the North edge of the parking area for the NYU Langone hospital. You will see the Long Island City sign, the Pepsi Cola sign and all of the new skyscrapers going up along the waterfront.