Located on the far side of the center of the galaxy, the Far 3kpc Arm stretches from one end of the Galactic Bar to the other. Star density is very high here, making route plotting difficult. It is also a region rich in nebulae.
Along with the Near 3kpc Arm, the counterpart 'inner arms' form a simple symmetry around the galactic center. These semi-elliptic arms are defined by shocked interstellar gas flowing along both sides of the galactic bar. This feature makes the inner arms essentially different structures than the spiral arms of the galaxy, since the spiral arms are not caused by an actual flow of materials but rather by density waves in the interstellar medium.
This perimeter of shocked interstellar gas is also what defines the boundary of the Galactic Core Regions - or simply, 'the galactic core'.