Grm Castle, Renaissance castle in Novo Mesto, Slovenia

Grm Castle stands on a gentle hill on the southern edge of Novo Mesto. It began in 1586 as a square tower with a single-storey wing, and later additions gave it a rectangular plan around a central courtyard. The courtyard facade has arcades with stone columns, later walled in, and the tower's central hall keeps a painted ceiling.

Krištof Mordax, a nobleman from a Carniolan-Carinthian-Styrian family, had the castle built in 1586. His son Hans Andreas added a storey to the right wing after 1636, and his grandson Wolfgang added the north wing and a high stone wall on the south side. In the 1880s the Carniolan provincial authority took over the castle and housed a newly founded agricultural school there from 1886 to 1990.

The only surviving painted interior is the ceiling of the central hall in the castle tower, framed by 17th-century stucco borders and filled with scenes of battles against the Turks. In the middle sits a field with the coat of arms of the Mordax and Gallenberg families. Valvasor noted that the castle once had richly painted rooms.

Grm Castle stands on a gentle hill on the southern edge of Novo Mesto, above the Krka. The building now houses the Novo Mesto unit of the Historical Archives of Ljubljana and the Institute for the Protection of Cultural Heritage, so the interiors are normally visited for official business rather than as a museum. In summer, social and cultural events take place at the castle.

The ceiling of the central hall in the castle tower is painted with military scenes framed by 17th-century stucco, with the coat of arms of the Mordax and Gallenberg families in the centre. This is the only surviving painted interior mentioned by Valvasor.