You are looking for a cache just off Norris Peak Road. Along this area these rocks have always reminded me of castle walls, hence the name. Please do not park on the road to attempt this cache, go instead to the parking coordinates given.
You will have about a quarter mile hike in fairly rocky conditions. This area seems to be marked for logging in the future, but all is quiet now. As you approach the cache, you can walk atop the castle wall; be careful as you are quite a way above the ground. If you continue along the ramparts after finding the cache, you will be rewarded with a nice vista (snowy today) of the Black Hills. These walls are high,so use caution when attempting this cache in snowy conditions as the rocks may be slippery.
This cache is well hidden and you may have to search a bit for it. I marked and averaged the waypoint four different times and these coordinates seemed the closest. Please rehide the cache well after finding it.