Mir-2 was a space station project begun in February 1976. Some of the modules built for Mir-2 have been incorporated into the International Space Station (ISS). The project underwent many changes, but was always based on the DOS-8 base block space station core module, built as a back-up to the DOS-7 base block used in the Mir station. The DOS-8 base block was eventually used as the Zvezda module of the ISS. Its design lineage extends back to the original Salyut stations.