Ruins, Hidden Treasure, You Know...
Treasure hunt Skellige suggested level 18
From the journal
Geralt found a map on the isle of Undvik with a key attached to it and a location deep in the isle's interior marked on it. This had all the makings of a fine treasure hunt.
Geralt journeyed to the location indicated on the map and found the ruins of an old fortress. Within them: a chest full of treasure - just as he had suspected.