Nykvarn Municipality is a municipality in Stockholm County in east central Sweden. Its seat is located in the town of Nykvarn. Nykvarn is a youn…Nykvarn Municipality is a municipality in Stockholm County in east central Sweden. Its seat is located in the town of Nykvarn. Nykvarn is a young municipality, and is the result of the splitting of Södertälje Municipality in 1999. Nykvarn can be regarded as a totally new municipality, because there was never before an entity with that territory or that name.