Inside the base are two S-ramps carrying Park Avenue to the Park Avenue Viaduct.
The western ramp carries southbound traffic and the eastern ramp carries northbound traffic, The two arcades are located on the outside of the ramps, connecting 45th and 46th streets.
The arcades contain shopfronts on the sides facing away from the viaduct's ramps: the west side of the western arcade and the east side of the eastern arcade.
The arcades are connected to Grand Central North, a system of passageways that lead to Grand Central, which opened in 1999.

The lobby is located in the median of the two ramps between 45th and 46th streets, with passageways to either side of the roadways.
The interior is designed to evoke New York Central's "prowess".
This is evidenced in the walls, which are made of marble, as well as the detailing of the bronze, where the railroad's initials are repeated many times.
A vestibule leads from 46th Street and contains multi-pane windows, bronze doors, a chandelier, and a pair of flanking vestibules with small storefronts.
Another nearly-identical but smaller vestibule on the southern end, near 45th Street, leads to the western walkway.

The lobby itself contains bronze chandeliers and an elaborate cornice with brackets and friezes.
There are thirty-two elevators, grouped in eight banks of four, labeled "A" through "H".
The elevator banks are double-height arched vestibules, with marble frames around the elevator openings, as well as bronze-ornamented elevator indicators.
The elevators contain elaborately decorated bronze doors painted "Chinese red", with the railroad's initials.
The elevator cab interiors contain Chinese red walls with wood moldings, as well as ceilings with gift domes and painted cloudscapes.
The elevator banks and cabs are similar, with minor variations.
Inside the base are two S-ramps carrying Park Avenue to the Park Avenue Viaduct. The western ramp carries southbound traffic and the eastern ramp carries northbound traffic, The two arcades are located on the outside of the ramps, connecting 45th and 46th streets. The arcades contain shopfronts on the sides facing away from the viaduct's ramps: the west side of the western arcade and the east side of the eastern arcade. The arcades are connected to Grand Central North, a system of passageways that lead to Grand Central, which opened in 1999.
The lobby is located in the median of the two ramps between 45th and 46th streets, with passageways to either side of the roadways. The interior is designed to evoke New York Central's "prowess". This is evidenced in the walls, which are made of marble, as well as the detailing of the bronze, where the railroad's initials are repeated many times. A vestibule leads from 46th Street and contains multi-pane windows, bronze doors, a chandelier, and a pair of flanking vestibules with small storefronts. Another nearly-identical but smaller vestibule on the southern end, near 45th Street, leads to the western walkway.
The lobby itself contains bronze chandeliers and an elaborate cornice with brackets and friezes. There are thirty-two elevators, grouped in eight banks of four, labeled "A" through "H". The elevator banks are double-height arched vestibules, with marble frames around the elevator openings, as well as bronze-ornamented elevator indicators. The elevators contain elaborately decorated bronze doors painted "Chinese red", with the railroad's initials. The elevator cab interiors contain Chinese red walls with wood moldings, as well as ceilings with gift domes and painted cloudscapes. The elevator banks and cabs are similar, with minor variations.
Helmsley Building