The remains of the Castle can be visited
Oybin Castle

The Oybin Castle Ruin is on a prominent mountain in the Zittau Mountains. Once planned as an imperial retirement residence and later complemented by a monastery, the complex is now a ruin.
History+
Archaeological finds prove settlement on Oybin mountain as early as the Bronze Age, long before the first structural elements of a castle appeared in the 13th century. This early complex was destroyed by Zittau in 1291 because it served as a base for robber knights. A reconstruction soon followed, and between 1311 and 1316, the castle was expanded into a fortified section castle under Heinrich von Leipa to protect trade routes. In 1346, it fell to the Bohemian Crown. Emperor Charles IV had the Kaiserhaus built from 1364, intending to use it as his retirement residence.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Uwe Klimpke
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: 50.8440, 14.7413