Susan C.
Yelp
While called a castle, the facade of this historic landmark appears more like a country mansion than a castle in the traditional sense. It's built in a Tudor Revival style, started construction in 1914 and completed in 1917. It's not small with a total of 176 rooms, though only about 20 are open to the public.
Tickets are available in person and in advance online and are recommended since they time the flow of people entering to not overcrowd the limited space inside. If you purchase the Sansoucci+ package, basic entry is also included. Aside from basic entry, separate tickets for tours are roughly once every 30 minutes, have limited language availability depending on the time, and book up quickly. I'd also suggest booking these in advance because when I arrived around 11:30am on a Saturday, times thru mid-afternoon were already full. Ticketing staff is able to assist in English if needed, though the attendants in individual rooms spoke German only.
Inside in the viewable rooms, there were descriptions in both English and German, however info was limited to 1-2 placards per room. Like some other reviews have mentioned there's not too much in-depth info you'll get by viewing the rooms yourself unless you download the app which provides a guided tour in a language of your choice. WiFi is available and free.
The path of the rooms can be completed in roughly 30 minutes, and the rooms themselves weren't super impressive aside from showcasing some period furnishings from the early-mid 20th century. I do agree it was poignant to see the meeting place where the end of WWII was discussed though.
A cafe and small gift shop are set up on the premises. Bathrooms are available both inside after the exhibits and outside prior to entering. Parking lots or structures aren't really available close by, I saw some people parking on the street side along the residential streets about a 10 min walk away and walking over though.
Surrounding the castle are green spaces with trails, suitable for a 30-40 minute stroll with man's best friend or a leisurely jog if you live in the neighborhood.