Incredible place! There are many options to visit the castle. I went twice and so I took two different ones. The most common is hiring a guide that will take you around the castle and tell you stories about it. If the group is large or if you don't really care much about knowing all the details then take this option. But if you really want to know everything, then I recommend you rent a small device that you can hung on your neck that will be telling you all about the castle. This option is for people with a lot of time as you'll be listening for about 1 and a half hours or more. This device is available in many languages and you can rent it by the side of the place where you buy the tickets to get inside the castle.
Oh! Don't forget to go down under the castle through the tunnels, search for the hidden one located to the right of the entrance, it will take you down under where there are no more lights, the air smells funny and there is water on your feet (take a lamp with you, iPhone's light isn't good enough).
This review is the subjective opinion of a TravelPod member and not of TravelPod.com.