The phrase 101st kilometre (Russian: 101-й километр, sto pervyy kilometr) is a colloquial name for the law restricting freedom of movement in the Soviet Union. The phrase was first coined after the 1980 Moscow Olympics when all "undesirable elements" (loiterers, prostitutes, alcoholics, etc.) were forcibly removed beyond the Eastern boundary of the Moscow Oblast, which lay 101 km from Moscow.
During most of the Soviet era, criminals and other undesirables, including supposedly rehabilitated political prisoners returning from the Gulags, were often banished from urban centers such as Moscow. It was intended in part to keep undesirable elements away from foreigners, who were usually restricted to areas within 25 km (16 miles) of city centers.
The rights of an inmate to move freely about the country after release from a prison would be restricted for a long period. Instead of regular documents, inmates would receive a temporary substitute, a "wolf ticket" (Russian: волчий билет, volchiy bilet), confining them to internal exile without the right to settle closer than 100 km (62 mi) to large urban centres where they would be refused the residency permit (propiska).
In modern Russia, this 100 km restriction has been abolished — although a version of propiska still remains — and the expression is used in a context similar to that of boondocks. The cultural divide by the 100 km line though still exists in Russia to some degree.