[1] It is one of the city's main thoroughfares, carrying traffic from Ville Haute, through Kirchberg, to a junction with the A1.

For the north-eastern three quarters of its length, on the eastern side of the Alzette, it bears the name Avenue John F. Kennedy.

At its southern end, in south-western Ville Haute, the N51 meets the N4 at an intersection.

From here, it heads northwards, followed by northeastwards, skirting the western edge of Ville Haute.

After bending almost a full right angle, it crosses the Alzette river, being carried over Pfaffenthal by the Grand Duchess Charlotte Bridge.