The remains of the Castle can be visited
Grünenberg Castle (Ruin) (Hitzkirch)

The Grünenberg Ruin in Hitzkirch is a castle ruin in the Lucerne Seetal, which once held a strategically important position.
History+
Grünenberg Castle was built in 1237 by the Counts of Kyburg. Its construction was closely linked to the development of the trade route through the Seetal to Lucerne and further over the Gotthard Pass. The castle controlled the surrounding area and secured sovereign rights in the upper part of the valley. Around 1360, the complex came into the possession of the Lords of Lieli. In 1386, Grünenberg Castle, along with the settlement of Richensee below it, was destroyed by the Lucerners in the run-up to the Battle of Sempach.
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: 47.2215, 8.2550