Industrial plant "Jupiter".
Initially "Jupiter" was involved in the production of electronic components for radios, but after the evacuation it was taken over by the company "Specatom" and worked for many years as a radiological laboratory.
It's better not to go down to the basements.They're almost completely flooded, and many theories suggest that the "Jupiter" was involved in the recovery of plutonium for the military. How much truth is in it? Who knows.