text: Doing some research it seems that "Ljanselva miljøpark" is a name given to the green area/route going along the river Ljanselva. See:
  https://www.skiforeningen.no/utimarka/omrader/sormarka/sykkelruter/hauketo-skullerudstua-ljanselva-miljopark/
  and https://www.osloelveforum.org/ljanselva/kartkultursagstua/
  
  This is not actually a park in the traditional sense, and should not be tagged as a park. I don't even know if it should be tagged at all, except for marking the various info signs and maps along the route, which has already been done at one place: https://www.openstreetmap.org/#map=19/59.86195/10.83493