When a companion tunnel to the Holland was proposed in 1930 to connect New Jersey with the island of Manhattan, the major problem wasn't where to build the entrance (Weehawken made the most sense for a variety of reasons) so much as it was how to get cars into it - Weehawken is built predominantly at the top of a series of granite cliffs several hundred feet high, while the tunnel entrance had to be close to sea level. The Helix is the answer.
Built simultaneously with the first of the Lincoln Tunnel's three tunnels, The Helix is a 6-lane highway that gracefully turns 360-degrees (though it doesn't look like it) while dropping from the Weehawken heights to the tunnel entrance. It's a massive wrought iron and concrete structure that hasn't changed all that much since its completion in 1937.
The thing that most people notice while traveling the Helix is the view, and what a view it is. As the road starts its descent, a wall of rough-hewn granite rises on the roadway's left-hand side and suddenly disappears to reveal a view of the Hudson River and the skyscrapers of Manhattan beyond. It's such an inspiring scene (and such a relief to commuters that it is routinely called the only good thing about their drive to work) that the view from the helix is protected as a landmark to prevent any new construction from obscuring the view.