This is the chief attraction of Kassel, and you will want to spend a minimum of 3 hours taking in all its attractions. (Sometimes visitors, mainly German, spend all day exploring the park.) Europe's largest hill park, Wilhelmshöhe sprawls across 350 hectares (865 acres) at the western edge of the city, a magnificent garden with 800 species of trees dating from 1701 when it was laid out in the baroque style.

The crowning achievement is the Statue of Hercules at the highest point of the park. This giant is a copy of a statue originally created in 1717, and it's mounted atop the castle-like octagonal base. You can climb the stairs of the base for one of the greatest panoramas in the area. Try to time your visit for a Wednesday or Sunday afternoon at 2:30pm from mid-May to September, when water gushes down a series of cascades from a fountain below the statue. The total height of the monument is 72m (236 ft.).

Also in the park stands Löwenburg (Lion Fortress), a faux castle from 1800, which was constructed at the height of the sentimental Romantic period. The castle contains a collection of medieval armor and weapons along with tapestries and antique furniture.

The Schloss itself, completed in 1803, is in the neoclassical style. Built on a wooded slope where a monastery once stood, it was the summer residence of the landgraves and the electors of Hessen-Kassel. For 7 years, it was the residence of Napoleon's brother, Jerome, during the Napoleonic era, and it also became the summer palace of Kaiser Wilhelm II. Napoleon III was imprisoned here from 1870 to 1871.

The state apartments are lavishly furnished with antiques, including the Kassel Apollo, a statue from the 2nd century A.D.

The main reason to visit is to see the Old Masters Gallery, a treasure-trove of art collected by the landgraves. The collection features 11 Rembrandts, including a trio of self-portraits of the artist. Other highlights include Dürer's Portrait of Elizabeth Tucher and landscapes by Jan Bruegel. The Italian School is represented by works by Titian and Tintoretto, with the Spanish School featuring paintings by Murillo and Ribera. There are also eight paintings by Rubens and seven by Frans Hals.

The city arranges summer concerts in the park.