Seen here are the underground resevoirs underneath the Palace of Versailles. Once a year on ‘maintenance day’, the water parterre reservoirs are emptied a few weeks before the Fountains show.

The Château de Versailles, which has been on UNESCO’s World Heritage List for 30 years, is one of the most beautiful achievements of 18th-century French art. The site began as Louis XIII’s hunting lodge before his son Louis XIV transformed and expanded it, moving the court and government of France to Versailles in 1682. Each of the three French kings who lived there until the French Revolution added improvements to make it more beautiful.

The château lost its standing as the official seat of power in 1789 but acquired a new role in the 19th century as the Museum of the History of France, which was founded at the behest of Louis-Philippe, who ascended to the throne in 1830. That is when many of the château’s rooms were taken over to house the new collections, which were added to until the early 20th century, tracing milestones in French history. [Source]