Lovely accommodations adjacent to an historic castle. I stayed in a single room on the 4th floor (a.k.a. "attic space") which was perfect for a solo traveler. This compact room offered excellent views of the Rhine River too. One thing about the 4th floor though, you will have to walk up from the 3rd floor as there is no elevator service to the 4th floor. If that is an issue, then simply book a room on the lower floors. The restaurant is excellent but can be busy, so reservations might be necessary on weekends during high season. Breakfast is included and superb. Additionally, their popular outdoor patio cafe with views of the river is ideal for lunch and/or drinks.
One caveat though: Sankt Goar is a small town and there is only one taxi service available. Should you need a ride to the top of the hill then it will cost you nearly 5 euros! While there is a 3 euro shuttle bus available, it runs only from 10:00 until 17:00 -- after that you are on your own. And trust me, walking up the hill with your bags is a challenge -- been there and done that. Down the hill is easy though.