This cave has an outstanding profusion of concretions with varied shapes (drapes, waterfalls, small columns) and colours, (white, brown, blue, pink) on three levels. A gallery-staircase with over 120 steps brings visitors back above ground.

The first castle, from 1051, was rebuilt by the Bishop of Liège in 1523, then destroyed by the French in 1703. Its present appearance dates from the Dutch occupation (1818-1821). The citadel was turned into a museum, with reconstructions, dioramas, miscellaneous items and a small weapons collection recalling the main events of its history and that of the town. The walls, 100m above the Meuse, offer a view of the town, the collegiate church and Meuse Valley.

This park flowing with water, compromising between formal French-type and romantic Italianate gardens, was conceived in the late 18C by one of the Montpellier family (owners of the estate since the 17C) members. It charms visitors with numerous and imaginative groves and fountains. It is pleasant to stroll beneath its century-old foliage, along the Buffet d'Eau fountains, the Petit Canal and upper Grand Canal, lined with lime trees.

The château perfectly complements the park and the upper parts of the walls of its oldest section (1627) are adorned with a pink brick pattern. It was enlarged in 1775, when the gardens were also created. The interior includes a series of rooms decorated with 18C woodwork, where family portraits and bouquets convey a refined atmosphere. The very fine music room has stuccowork by the Moretti brothers and offers beautiful views of the garden.

The Tour Joyeuse, once part of the former Counts Castle, is on the right climbing up the Route Merveilleuse. A terrace in the north-east corner of the rocky spur offers a beautiful panorama of the Sambre and Meuse valley. The road then reaches the Keep, runs between two of the former castle's towers and crosses the moat to the fortress. The 15C and 16C Mediane bastion and 17C Terra Nova bastion have a complex defensive architecture.