The Valleys, the Corniche and Luxembourg's UNESCO Heritage
Luxembourg City's most distinctive natural feature is the system of deep river valleys - the Pétrusse and Alzette - that cut through the plateau on which the city stands, creating a topography of dramatic cliffs, viaducts, and lower quarters that gives it a character unlike any other small European capital. The Chemin de la Corniche, running along the cliff edge above the Alzette valley with views across to the Grund quarter below and the fortification walls built into the rock face, has been described as the most beautiful balcony in Europe and is the single most rewarding walk in the city. The Bock Casemates, a network of underground tunnels carved into the rock of the Bock promontory between the 17th and 19th centuries and used as shelters for the civilian population during sieges and both World Wars, can be explored on self-guided tours through 17 kilometres of galleries cut directly into the sandstone cliff. The Grund quarter below, one of the lowest points of the city and historically its working quarter, has been transformed into a neighbourhood of restaurants, bars, and cultural spaces while retaining its medieval street pattern and abbey buildings. The city's fortifications, which were among the most formidable in Europe before their partial demolition under the 1867 Treaty of London, are collectively recognised as a UNESCO World Heritage Site and form a heritage trail that connects the Bock, the Spanish Tower, and the surviving wall sections above the valleys.