Answer:
The Bronx is just north of Manhattan. The two boroughs are separated by a skinny stretch of river that branches off of the Hudson River, called the Harlem River. Several subway lines run between Manhattan and the Bronx: the 4-5-6 (the green line), the 1 and 2 of the 1-2-3 (the red line), and the B and D of the B-D-F-V (the orange line). See the Related Link below for a complete New York City subway map.