This remains of this large fortress is a nice stop with younger children, as it is an outdoor, self-guided tour through the large grounds where kids can run and get out some energy while exploring. Some areas require moving through dark tunnels, so bring your cell phone as a flashlight and really have some fun! The grounds began as the Rheinfels Castle in the mid-1200s and was the residence of counts before becoming a fortes and military complex. When the castle fell to the French, Prince Wilhelm of Prussia acquired the ruins and today can be viewed daily from mid-March through November and weather-permitting during winter weekends.