The remains of the Castle can be visited
Forstenberg Castle (Ruin)

The Forstenberg ruin, once a high medieval noble castle, is located near Karlstein, a district of Regenstauf in the Bavarian district of Regensburg.
History+
The origins of Forstenberg Castle presumably lie in the 13th century, when it was built by the Lords of Forstenberg, ministerials of the Lords of Hohenfels, as their ancestral seat. After 1330, the castle passed into the possession of Friedrich dem Hofer, who from then on called himself “von Vorchtenberg”. In 1393, Landgrave Johann von Leuchtenberg acquired the complex, who was also responsible for the construction of Karlstein Castle. Under his aegis, the construction of an outer bailey began, which remained unfinished, as the castle passed to Jakob Muracher as early as 1404. Heinrich Zenger acquired Forstenberg in 1460, along with Karlstein Castle. The expansion of Karlstein Castle likely led to the gradual decay of Forstenberg Castle, which was finally abandoned by the 17th century at the latest.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 49.1515, 12.1642