The palm greenhouse (sometimes called the orangery), located in the upper part of the castle park, is an extraordinary architectural gem that boasts not only its unmistakable beauty but also its rich history.

The building was built in the Classicist style at the beginning of the 19th century, at the time when the then owner of the Opočno estate, Rudolf Josef Colloredo - Mannsfeld (1772 - 1843), had the adjacent park landscaped in the spirit of nature.

The south-eastern wall of the building, which is open to the park and is 50 m long, illuminates the main areas of the building. It consists of a richly decorated wooden structure with cast-iron and glass elements - slats.

The greenhouse still serves its original purpose, to grow and overwinter exotic thermophilic plants such as citrus, olive, palm, oleander and others. From May to October, these plants decorate the palace chambers and courtyard.

Adjacent to the greenhouse is a building originally used as a gardener's house. During the First Republic, the main entrance to the garden was established here. A fee was charged for entry. It is now a public library.

The upper part of the park, into which the greenhouse is composed, is considered to be the longest used garden. Already in the 16th century, vegetables and spices were probably grown here for the castle kitchen and there was undoubtedly an ornamental and fruit garden.

The greenhouse is open to the public occasionally, e.g. during exhibitions.