Mir, DOS-7, was the first module of the Soviet/Russian Mir space station complex, in low Earth orbit from 1986 to 2001. Generally referred to as either the core module or base block, the module was launched on 20 February 1986 on a Proton-K rocket from LC-200/39 at the Baikonur Cosmodrome. The spacecraft was generally similar in design to the two previous Soviet orbital stations, Salyut 6 and Salyut 7, however possessed a revolutionary addition in the form of a multiple docking node at the forward end of the module. This, in addition to the docking port at the rear of the spacecraft, allowed five additional modules (Kvant-1 (1987), Kvant-2 (1989), Kristall (1990), Spektr (1995) and Priroda (1996)) to be docked directly to DOS-7, greatly expanding the station's capabilities.

-Wikipedia