From the World Heritage inscription:
The Garden Kingdom of Dessau-Wörlitz is an outstanding example of the application of the philosophical principles of the Age of the Enlightenment to the design of a landscape that integrates art, education and economy in a harmonious whole.
The first essays in landscape design began with the foundation of Oranienbaum, with its unified layout of town, palace, and park from 1683 onwards. The resulting complete Baroque ensemble, with obvious Dutch connections deriving from its designer, Cornelis Ryckwaert, has survived to the present day. Further developments on these lines took place around 1700 with the reclamation of marshy areas along the Elbe and the creation of planned villages and farmsteads. During the reign of Prince Leopold III Friedrich Franz of Anhalt-Dessau (1740-1817), an extensive landscape design project was begun around 1765 over the entire principality. This ambitious programme was launched in close collaboration with the architect and art theorist Friedrich Wilhelm von Erdmannsdorff (1736-1800). Landscape design, public education, and encouragement of the arts were closely integrated in this scheme. Wörlitz became the point of departure for wide-ranging improvements based on English landscape gardens and neoclassical architecture.
This unified scheme of buildings, gardens, and works of art, with a pervasive educational theme became the outward expression of the Enlightenment. Schloss Wörlitz was built in 1769-73 and it was the first neoclassical building in Germany. The Gothic House (1774) established a vogue for Gothic Revival buildings all across Europe. A number of other landscape projects in the principality date from this period. One of the most innovatory was the Chinese garden at Oranienbaum (1790), based on the theories of the English architect Sir William Chambers.
The roads and dykes that were essential for infrastructural development were planted with avenues of fruit trees, giving them an ornamental aspect. By the time Prince Franz died in 1817 virtually the entire principality had become a unified garden. Despite industrialization and the consequent expansion of Dessau since 1900, the characteristic features of the landscape have been preserved.
There are two major things to see if you visit Wörlitz: the palace and the park.
The palace is one of the better preserved buildings you will see in Germany. Not only was it (relatively) recently built in the 18th century, but it was untouched by WWII. It is also considered to be one of the first neoclassical buildings in Europe.
The park surrounding the palace is one of the best and earliest examples of an English garden in continental Europe.
Despite the name being “Dessau-Wörlitz”, the site is located in the town of Wörlitz, not in the nearby city of Dessau. It is very close to the Dessau part of the Bauhaus and its Sites in Weimar and Dessau world heritage site. Both can easily be visited in the same day.