Courtesy Flickr user Sybren Stuvel

The Chapel of Notre Dame du Haut, Ronchamp, in the foothills of the Vosges in France—as beloved as any icon in architecture—was vandalized last Friday night.

The Roman Catholic chapel, designed by Le Corbusier, is considered one of the architect's finest works and one of the most important pieces of religious architecture of the 20th century. Completed in 1954, the National Commission for Historic Monuments designated the chapel as historic site in 1967.

A nun from the nearby monastery of Poor Clare Sisters discovered the damage. Police arrived at the scene Saturday morning and confirmed that the damage was due to a forced entry via a door. A stained-glass window was broken and a concrete trunk was found outside the building.

The stained-glass window, declared "irreparable" by the department of historic monuments, featured an original illustration by Le Corbusier and signed by the architect himself.

Antoine Picon, president of the Fondation Le Corbusier, issued a statement, calling on the Association Oeuvre Notre-Dame-du-Haut to "better protect the heritage of the twentieth century and that of Le Corbusier in particular."

Today the building is a tourist attraction, drawing in approximately 80,000 visitors per year, and still operates as a site for religious services. However, the building is in "very poor condition," according to Picon, suffering from moisture problems, infiltration, and poor preservation of masonry.

"[The Le Corbusier Foundation] regrets that no specific measure has helped to secure the site and preserve one of the most iconic and most fragile elements of the Chapel," said the statement.