Starting with the north side and moving clockwise, its five façade entrances are the Mall Terrace, the River Terrace, the Concourse (or Metro Station), the South Parking, and the Heliport.[11] On the north side of the building, the Mall Entrance, which also features a portico, leads out to a 600 ft-long (180 m) terrace that is used for ceremonies. The River Entrance, which features a portico projecting out twenty ft (6 m), is on the northeast side, overlooking the lagoon and facing Washington. A stepped terrace on the River Entrance leads down to the lagoon; and a landing dock was used until the late 1960s to ferry personnel between Bolling Air Force Base and the Pentagon. The main entrance for visitors is on the southeast side, as are the Pentagon Metro station and the bus station.
There is also a concourse on the southeast side of the second floor of the building, which contains a mini-shopping mall. The south parking lot adjoins the southwest façade, and the west side of the Pentagon faces Washington Boulevard.
The concentric rings are designated from the center out as "A" through "E" (with additional "F" and "G" rings in the basement). "E" Ring offices are the only ones with outside views and are generally occupied by senior officials. Office numbers go clockwise around each of the rings, and have two parts: a nearest-corridor number (1 to 10), followed by a bay number (00 to 99), so office numbers range from 100 to 1099. These corridors radiate out from the central courtyard, with corridor 1 beginning with the Concourse's south end. Each numbered radial corridor intersects with the corresponding numbered group of offices (for example, corridor 5 divides the 500 series office block). There are a number of historical displays in the building, particularly in the "A" and "E" rings.[citation needed]