Schloss Eggenberg is a unique Baroque synthesis of the arts. Architecture and furnishings combine here to create a complex symbolic representation of the universe. It was planned and built by Prince Hans Ulrich and his architect Pietro de Pomis not only as an impressive representative building, but also as a comprehensive architectural allegory. In its entirety, the palace is a mathematically harmonious cosmos, an architectural image of the universe in which the learned architect formulated his idea of an orderly world in an era of chaos and dissolution. The residence of the imperial governor Hans Ulrich von Eggenberg is political architecture and a sophisticated legitimization of a family's rule.

The castle preserves a precious ensemble of historical interiors with an important cycle of over 500 ceiling paintings. It is an almost unadulterated work of spatial art, in which the interior design phases of the 17th and 18th centuries combine to form an ensemble of special experiential value.

Today, the castle is surrounded by an extensive landscaped park from the Romantic period, which is one of the most important gardens in the country with its valuable tree population.

The Beletage of Eggenberg Palace has retained its original appearance almost unchanged to this day. The cycle of 24 state rooms with original 17th and 18th century furnishings is one of the most important ensembles of historic interiors in Austria. Rarely has a room interior of comparable artistic quality been preserved so completely and so undisturbed. Its centerpiece is the splendid Planetary Hall, completed in 1685. With its multi-layered pictorial program, in which astrological and hermetic ideas, numerical symbolism and family mythology merge into a complex allegory for the glory of the Eggenberg family, it is one of the most impressive works of interior art of the early Baroque period in Central Europe.

In the 17th century, the Planetary Room was the atrium or entrance room to the princely apartments, which could only be entered by selected visitors in strict order of precedence; a circle of 24 state rooms, which originally probably formed two large suites - the 12 rooms on the south side for the prince and the 12 rooms on the north side for the princess. What they have in common is the sumptuous decoration with over 500 ceiling paintings in lavish stucco frames, which have been preserved to this day. Mythological scenes, ancient, biblical and modern histories are combined with allegories, emblems and vedute to create a Baroque pictorial cosmos.

In the last phase of the building's history, in the 18th century, the state rooms were given their current appearance. The masonry and interior decorations with three East Asian cabinets and charming painted genre scenes date from the Rococo period. The ceiling paintings from the 17th century were left untouched during the refurbishment.

Since its creation in the early 17th century, the Eggenberg Gardens have undergone many changes and reflected the tastes of the time. Only a few traces remain of the Baroque formal garden of the Eggenberg princes, which surrounded the palace with rich broderie parterres and hedgerow squares.

Today, the castle lies in an extensive landscape park from the Romantic period, which, with its valuable tree population, is one of the most precious garden monuments in the country.

In 1993, a park conservation project was commissioned in collaboration with the Federal Monuments Office with the aim of preserving and reconstructing the garden as a cultural monument of Romanticism. The aim was to preserve the valuable existing features and replace the lost elements as far as possible. Since 2000, extensive measures have been taken to supplement and reconstruct groups of trees and shrubs, the pond and visual axes. Further major steps in the restoration of the Eggenberg gardens were the restoration of the so-called "Herrschaftsgarten" at the rear of the palace and the garden in front of the south pavilion. With the reconstruction of the rose hill in the winter of 2007/2008, the historic garden site has been restored to its former glory. The evaluation of all sources, including the original order catalogs from the Biedermeier period, also made it possible to reconstruct the original planting. When the historic roses are in bloom (end of May to June), they form a glittering highlight of the garden, which is accompanied by special rose tours on the history and care of the plants.

In August 2010, the UNESCO World Heritage Committee extended the existing World Heritage Site "Graz - Historic Center" to include Schloss Eggenberg. It was proposed to add Schloss Eggenberg to the existing World Heritage inscription of the Old Town of Graz, as the castle and the Eggenberg family are inextricably linked to the history of the province of Styria and its capital. For centuries, the Eggenbergs exerted an important influence on the political and economic, but above all the artistic development of the city, to which their residence on the outskirts of the city bears the most significant testimony.

Schloss Eggenberg has thus been awarded the highest seal of quality that the international community of states can bestow on cultural monuments. It was included in the exclusive group of the world's outstanding cultural and natural sites which, according to the UNESCO World Heritage Convention, are not to be regarded as the property of a single state, but as the ideal possession of humanity as a whole.

Sites are selected for the World Heritage List solely on the basis of their significance as the best possible examples of the world's cultural heritage. Decisive for the status of Schloss Eggenberg as a work of spatial art is a cycle of 24 state rooms with the large Planetary Room at the center. In these rooms, the Baroque and Rococo periods of decoration combine to form an inseparable unit of the highest charm and undisturbed experience value from today's perspective. Above all, the huge cycle of over 500 ceiling paintings from the 17th century with its extremely sophisticated and complex pictorial program - a characteristic testimony to the early Baroque understanding of the world - is of singular importance. The quality and extent of the preserved, authentic substance of the Eggenberg Beletage are a particular stroke of luck, which is why the World Heritage Commission rated it as "excellent".