The Opeka Arboretum, or park – gardens along the castle, is an example of park architecture of high aesthetic and dendrology value. It bears the characteristics of a landscape and romantic garden, which the then castle new owner, Count Marko Bombelles, started landscaping mid-19th century, bringing many plant species from different parts of the world. Although initially not designed as an arboretum but rather as gardens connected to the castle, it became that for its rich dendrology collection. It remained preserved to date, with here and there some original stone benches still preserved as a valuable sculptural ornament to the park. In its form, the Arboretum covers a plain surface where the castle and park-shaped gardens are located, and a hilly environment with forest vegetation known as park-forest and lake. A deliberate and elaborate horticultural design shows a refined relation between architecture and the inseparable surrounding area. All landscape elements, such as modifications to the forest area and open surfaces, solitary trees of stunning shapes, various dendrology species and a small lake with an island, contribute to the beauty of the landscape composition with numerous vistas and views typical of landscape style gardens. It is precisely by a deliberate application of various plant species that a unique formative expression was created by which the gardens were known throughout Europe. By decision of the National Institute for the Protection of Natural Values of 1947, it was proclaimed a protected natural rarity

In 1961 it was proclaimed a monument of garden architecture - arboretum. When the Arboretum was ceded to the Gardening School for use, it cared for it in line with its always modest resources. In 2003 the Republic of Croatia becomes the owner of the Arboretum and the castle.

The Opeka Castle, situated within the Arboretum, is located 18 km west of Varaždin in Marčan. In its original form, it was erected as a baroque three-wing mansion, to later undergo numerous alterations, especially in the period of historicism in the second half of 19th century. The castle was originally built in the 17th century, with Counts Keglević being mentioned as first owners, according to the inscription at the entrance to the castle. In the 18th century the castle belongs to the Drašković noble family, while later, from mid-19th century to the end of World War II, to the Bombelles family, credited for the definitive design of both the castle and the garden - Arboretum. The baroque castle was built as a U-shaped structure and in the period of historicism a small wing was built in to the main corps in the northwest part of the castle, terraces and towers were erected on the main, southeast facade, and the façades of the inner courtyard got arcade corridors. On the southeast façade facing the park, there is a central avant-corps with a trifora on the 1st floor and the noble family coat of arms underneath, flanked on both sides by terraces above the arcades. Quite a lot has been preserved of the original stone architectural plastics, such as stone window frames, portals, stone corbels with attic coronals, staircases, coats of arms of the Drašković and the Bombelles. Very interesting are also old stone Roman monuments embedded as spolia in the structure of the walls.

A field workshop will be organized in the Opeka Arboretum on the topic of fauna and flora biodiversity. Kindergarten and elementary school children as well as high school young people will participate to the workshop in order to become aware of the importance of preserving the natural and cultural heritage surrounding us. The aim is to raise awareness among all local community members about the importance of the natural and cultural heritage they live in.

The programme takes place under the auspices of the Municipality of Vinica.