Available in winter, but nicest in summer.
Between Trondheimsveien and Rødbergveien is a small green stripe
with a tiny creek sizzling through it and the place is called
"Bekkedalen".
Valley and river against the motorway(photocredits PPJ):

See: "http://www.osloelveforum.org/hovinbekken">Osloelveforum
for more info.
At both ends of the path there are infosigns giving you an
introduction to this rather rare microenvironment.
The new cache is a black canister,
slightly smaller than a matcbox containing:
1 combined infonote and log. And a pencil.
New hints as of April 12 2006!