The location:
Grímsnes is a very popular area for summer(or winter) cottages in Iceland. When driving to Gullfoss and Geysir you pass this area. Kiðjaberg is most known for its golf course wich is located in a great landscape. The river Hvíta runs by it and lake Hestvatn is also nearby. From the hill where the cache is you can see an amazing view over the river and the golf course on the other side.
The cache:
From the ringroad nr. 1 you take road nr. 35 and drive for about 10 minutes until you see a sign to Kiðjaberg. From the turn there is a few minutes drive until you see the Kiðjaberg golf course club house. To the right of the club house there is a road leading to a parking spot where you should park your car. You walk the path that goes up the hill, but don't go all the way, the cache is below the hill to the left of the path.
The cache is a glass jar with a logbook, pen and some small toys for change
I highly recommend that you go all the way up the hill after finding the cache. The view from there is amazing.