A world heritage site, the cathedral is one of the most remarkable works of art of Gothic architecture. It has numerous stained-glass windows and rose windows, of which two each measuring 13 metres in diameter are among the largest in Europe. Its construction in the Middle Ages spanned almost two centuries, from the 13th to the 14th century; in the 19th century, after the French Revolution, restoration work was supervised by the architect Viollet-Le-Duc. Its gargoyles, steeple, towers and bells inspired one of the most famous novels by Victor Hugo, Notre-Dame de Paris. Situated in the historic centre of Paris at the end of the Ile de la Cité, it is the symbolic heart of Paris and all road distances in France are measured from a point on the cathedral forecourt. Renowned throughout the world for more than five centuries, it welcomes as many as 50,000 visitors on certain days. There is a programme of sacred music throughout the year. Open daily, entry is free. There is a charge for visits to the towers.