You can call this town Sarov. It was codenamed and identified Arzamas-16 by Russian government between 1946-91. Then it was called as Kremylov until 1995.
This town is the place that gave Russia its saint- St Seraphim. But its streets have more or less remained closed to the general public in the past six decades. You need a permit to enter Sarov.
Sarov was kept so secret that it remained unmarked on the Russian map. The Russian government and agencies had a reason to keep it a dark secret. Sarov was the where Russians placed their Nuclear Research Facility.
Surrounded by barbed wires to keep peeping Tom's away, and, armed guards to restrict people' movement, Sarov was the place that produced erstwhile USSR’s first nuclear bombs.
Naturally, internet access to the town was restricted heavily. But, thanks to a bunch of bitcoin crazy scientists, internet access to the town's central computing facility was opened, albeit briefly.
The super-computers at the research facility, able of processing trillion calculations every second, were used to mine bitcoins by these scientists.
In fact, the facility that employs close to 20000 people has a processing capacity of 1 petaflop. 1 petaflop is equivalent of 1000 trillion calculations per second. To give you a comparison, a normal computer with an X86 system architecture could offer 100 billion instructions per second.
The Russian nuclear agency had purposely kept the computers off the internet grid in order to maintain privacy of secret files. Russia's Federal Security Service was quoted in a press release saying that the computers were not supposed to be connected to the internet to prevent intrusion.
The Russian agency has now managed to shut internet services and is pursuing criminal cases against the scientists, for using the country's nuclear facility for personal purposes.