The cache is placed close to where Styggedalsbekken from the Frognerseter area and Skådalsbekken make a joint just north of Holmendammen. 115 meters above sea-level.
The view from the cache, at night:

Theme: Waterways of Oslo - creeks and rivers /
Tema: Oslos vannveier - bekker og elver
These geocaches are placed along the waterways of Oslo (from west to east and downstream): /
Disse geocacher er plassert ved Oslos vannveier (rekkefølge fra vest til øst og nedstrøms):
~ Heggelielva: PPJ #15 Heggelielva, Gryta
~ Tverrelva: PPJ #27 Midtre Lysedammen
~ Sørkedalselva: PPJ #14 Overfloden, river of Oslo
~ Lysakerelva: PPJ #18 Peter's Crossing, Lysakerelva Spilleboksen,
Lysakerelva Offpiste #1, PPJ #43 Wet Arena,
SQUAWK#1 The New Bridge at Fåbro and SQUAWK#2 The Mill Falls of Lysaker
~ Mærradalsbekken: PPJ #26 Sneak Creek
~ Styggedalsbekken and Skådalsbekken: PPJ #22 Twin Creeks
~ Hoffselva: PPJ #19 Court Creek Coming
~ Sognsvannsbekken: PPJ #2 Sognsvannsbekken creek
and HYSSE#19 "Spring Cache"
~ Frognerelva: Oslo West No 10 - The Park 1/4 and PPJ #42 Frognerelva Exit
~ Akerselva: Drama Behind You, Triple Islands, PPJ #23 Borderline North,
As Close As You Get, PPJ #44 Aamodt Bru and AG#24 - Canvas Fall
~ Hovinbekken: HYSSE#9 "GreenTrashCache"
~ Alna: Lillomarka Rundt #3 - Alna, AG#17 - The old bridge of Alna,
Alnaparken, AG#23 - Cotton Fall and HYSSE#5 "A RiverDance"
~ Haugerudbekken: AG#8 - Soda creek
~ Østensjøbekken: AG#6 - Silent creek
~ Ljanselva: Rotten Bastard
Seven rivers in Oslo are falling into the Oslo Fjord:
Lysakerelva, Mærradalsbekken, Hoffselva, Frognerelva, Akerselva, Alna and Ljanselva
Styggedalsbekken from the Frognerseter area and Skådalsbekken make a joint just north of Holmendammen, from where Holmenbekken runs into Smedstaddammen pond. Hoffselva starts its journey into the Oslo Fjord from Smedstaddammen.
Makrellbekken joins Hoffselva south of Smedstaddammen.
For more info in Norwegian, see: Oslo Elveforum, Hoffselva
The cache is supposed to be well hidden!
Please reinsert it so and make sure it is covered for running water.