The biggest and the most expensive of all the Babylon stations, Babylon 4 was built by Earth Force Science & Technologies Division. It was the first of the Babylon Stations to be completed - the previous three stations were sabotaged and destroyed early in construction (Babylon 1 & 2 by the collapse of their infrastructure caused by sabotage, while Babylon 3 was blown up after being constructed of inferior materials, as a trap to whomever had destroyed the two proceeding stations). Some of the leftover parts from the previous three attempts at constructing a station were used in the making of Babylon 4.

Much of Babylon 5 can be seen in its predecessor, although Babylon 4 with a length of about 9300m was the biggest complex ever built by mankind. It had a second, slightly smaller section constructed around the rotating part of the station, only rotating in the opposite direction, which could provide a higher gravity environment as well as essential extra stabilization for the station should it be moved forward using its rear mounted engines.

Other differences were in its aft mounted fins which were arranged radially, with the flat edges pointing forwards like petals of a flower rather than arranged in four rows of three. The front section which was considerably longer than in its predecessor, and the docking booms were located along the sides of the station rather than at the front as in Babylon 5.

Babylon 4 was designed to provide living space for about 500,000 life-forms during normal traffic (as against Babylon 5's 250,00 maximum), and up to 1,000,000 life-forms at peak times.

Babylon 4 disappeared from its construction site in sector 14 without a trace in 2254, a mere 24 hours after becoming operational, along with a skeleton crew of around 1,200 personnel under Major Lewis Krantz, an event observed by departing construction workers, including Thomas Jordan, aka Jinxo [season 1 "Grail"]. The station was listed as destroyed by Earth Force. The station made a brief reappearance in 2258 after its disappearance, when its initial crew was rescued by a team from Babylon 5 led by Jeffrey Sinclair and Michael Garibaldi, after which Earth Force confiscated all records of events in sector 14, and marked the sector as off-limits. However copies of the events were kept surreptitiously by Michael Garibaldi.

Reports submitted by Major Krantz indicated that the station had just become operational when discrepancies started showing up in the stations' time-tracking systems, initially thought to be a computer glitch but later found to be a time anomaly when the crew started seeing glimpses of the past and what was assumed to be the future. The confusion was compounded when a mysterious being, calling himself Zathras appeared out of nowhere claiming to be looking for someone identified only as "The One" who was a leader in a great war between the forces of light and dark.

In 2260 it was revealed by Delenn that the station was being stolen and transported through time to be used as a replacement base of operations in a the previous Shadow War by Zathras and a past version of Jeffrey Sinclair, Valen, after the Shadows had managed to destroy the Minbari space station that had been the command center.

Leaving Michael Garibaldi behind at Sinclair's behest Delenn, Sheridan and Sinclair left on the White Star, accompanied by Susan Ivanova, Marcus Cole and Lennier. Draal, the Keeper of the Great Machine, had opened a rift in Sector 14 to transport the White Star to 2254 where they destroyed several Shadow fighters attempting to use a fusion bomb to destroy Babylon 4. They were able to put in place the equipment necessary to move the staion back in time by 1000 years.

A premature initialization of the device when Major Krantz ordered an increase in the output from the station's power core moved the ship forward four years to 2258 where its initial crew disembarked for Babylon 5 after the arrival of the earlier Jeffrey Sinclair and Michael Garibaldi. With the station to themselves the necessary preparations were soon completed and Sinclair and Zathras took Babylon 4 back in time to fight in the previous Shadow War while the others returned through the time rift to 2260 on the White Star.

Having arrived in the past Jeffrey Sinclair, by now in Minbari form having using the chrysalis device, and backed by two Vorlons introduced himself as Valen and led an epic struggle that drove the Shadows back, although the station itself did not come out of the war in very good shape and did not survive much longer before breaking up.

"I welcome you and present this place to you as a gift.
I am called Valen, and we have much work ahead of us"

The communications ID code for Babylon 4 was  0010835-081677