An experimental nuclear reactor that was housed 25 meters under the campus of KTH Royal Institute of Technology in Stockholm.
That would be in the very inner city of the capital of Sweden. The reactor was active between 1954 and 1970.
It was the first Swedish nuclear reactor and the only one thus far to have been completely disassembled and decommissioned.
The many (compared to population and other energy resources) Swedish nuclear reactors (at least 14) suggests something about ambitions other than producing electric power.
The kind of ambition that requires weapons-grade plutonium to achieve.
…Reaktor 1, R1, startas, och klockan 18:59 den 13 juli 1954 gick reaktorn kritisk, det vill säga kärnklyvningen blev självgående.
…Reactor 1, R1, is started, and 18:59 the 13th of July 1954 the reactor becomes critical and manifests fission – a sustained and slow nuclear chain-reaction.