The first documented reference to the Gräpplang castle dates from the year 1249. It was built around 1220 by the Knights of Flums. During the Old Zurich War (1436-1450), the castle was extorted in 1440 to get protection, but it was never attacked or destroyed.
In 1528 the property was given to Ludwig Tschudi von Glarus. The castle remained in their family possession until 1767. The Tschudi family gave the castle its recognizable appearance. However, the construction work was carried out in poor quality which caused expensive maintenance work. As there was no interest in preserving the castle, it was sold for demolition in 1804. Recyclable materials such as bricks, iron mountings, fixtures, woodwork and building blocks were sold whenever possible.
In 1923, the ruins of Gräpplang Castle were taken over by the commune of Flums and during the following years, extensive building work was carried out to restore the castle. A few years ago the “Pro Gräpplang” foundation was formed, which organises cultural events in and around the Gräpplang ruins.
Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.