Starbase 84 was a Federation Template:ShipType starbase that was in service with Starfleet in the late 24th century. This starbase was capable of handling major starship refits, and was located near the Romulan Neutral Zone.
The USS Enterprise-D visited this starbase in 2364. (TNG: "Heart of Glory")
In 2370, a new warp core was installed on the Enterprise-D here. (TNG: "Phantasms")
The exterior footage of Starbase 84 was a reuse of footage of Starbase 74 from TNG: "11001001", which in turn was a reuse of footage of the Earth Spacedock from Star Trek III: The Search for Spock.