The exhibition gives information on the history and functioning of Paris's sewage system.

The sewers of Paris are no longer the cesspool in which Jean Valjean got lost in 1832. Since the era of Baron Haussmann, a well-maintained system has mirrored each Parisian street with its own subterranean gallery. The system consists of 2,400 kilometres of galleries maintained by the city's teams of sewer workers.

A computerized system for the management of Paris's sewage system called TIGRE centralizes all information on the physical state of the city's sewers, which the sewer workers verify on-site with the help of their portable computer terminals. They inspect each portion of the network at least twice a year.

Île Saint-Louis owes its most majestic buildings to the architect Louis Le Vau. The architect moved here with his family in the late 1630s and carried out, in addition to numerous private projects, the construction in 1644 of the Saint-Louis-en-l'Île Church. In 1664, the development of the island was practically finished.

The island was home to two types of population: often wealthy artisans and merchants who established themselves along the interior streets and figures of higher rank, nobles and upper middle-class persons, who preferred to have their townhouses built on the quays with their view of the Seine and the City of Paris.

Île Saint-Louis takes its current name from King Louis IX, also known as Saint Louis, the patron saint and ancestor of Louis XIII. As legend would have it, he often came to the island to pray and brought the cross here with his knights in 1269 before setting off on the eighth crusade, during which he would die in Tunis a year later.

Built from 1671 to 1676, first by Liberal Bruant, then by Jules Hardouin-Mansart and Robert de Cotte, Les Invalides is one of the most prestigious monuments in Paris. Today allocated to the Ministry of Defense but also occupied by numerous other bodies dependent upon a variety of ministries, Les Invalides still serves its first function as a hospital-hospice for the severely-disabled, soldiers wounded or mutilated during military service. In addition to the Musee de l'Armee, Les Invalides houses the Musee des Plans-Reliefs (a museum of military models) and the Musee de l'Ordre de la Liberation, as well as two churches: the Eglise du Dôme, housing the tomb of Napoleon I, designed by Visconti in 1843, and the Eglise Saint-Louis des Invalides. During the second half of the 20th century, the site of Les Invalides was opened up to the eyes of the public thanks to the destruction of the small rear buildings and the creation of a surrounding ditch. In 1981, a vast renovation programme was carried out under the instigation of an interministerial commission presided over by the Ministry of Defense and the Ministry of Culture, to restore the original splendour of this exceptional architectural grouping.