Yes, this is the real Castle Frankenstein. It’s just South of Darmstadt, Germany. The castle was build circa 1240 probably by Konrad Reiz von Breuberg, who is mentioned in the first document proving the existence of the castle in 1252. He and his descendants changed their names into von Frankenstein then. The hill whereupon the castle stands was probably occupied by another castle since the 11th century which fell into ruins after Castle Frankenstein was build a couple of yards to the northwest. Claims of an even older predecessor upon the hill are widespread but historically unlikely.
In 1292 Count William II of Katzenelnbogen forced to open the castle[1], meaning that he could use it in case of a military conflict, which actually never occurred, the castle was never under siege.
In 1363 the castle were split into two parts owned by two different families of the knights of Frankenstein. At the beginning of the 15th century the castle was enlarged and modernized. The Frankenstein Knights became independent from the Counts of Katzenelnbogen again.
The downfall began in the 16th century with the Protestant Reformation. The Landgraves of Hesse, who meanwhile owned most of the surroundings became Protestants while the Frankenstein Knights stayed catholic, and therefore isolating themselves. In 1662 they had to sell the castle and all their possessions to the Landgraves of Hesse-Darmstadt. The castle was used as refugee and a hospital afterwards and fell into ruins in the 18th century.
Two towers, which are so distinctive today, are a historical inaccurate restoration of the mid-19th century. In 1970 a restaurant was build within the castle. In 1976 American soldiers founded an annual Halloween festival at the castle which became to one of the biggest Halloween festivals of Europe.