JOINVILLE, France — The soft-spoken mayor of this ancient village on the Marne River put his hand on my arm as we shivered in the late winter cold in front of a narrow house. Snow dusted the rooftops, and hardly a soul was in sight on the cobblestone street.

“Are you ready for this?” asked the mayor, Bertrand Ollivier, his expression pained.

“It’s violent,” he said.

The mayor’s aide for urban planning, Anthony Koenig, his hands freezing, fumbled for the key to the 16th-century house and fitted it into the front door lock; the metal scraped in the gray silence.

He pushed it open: The violence was visible.

The floorboards were gone; the room once used as a kitchen was bare of tiles. Underfoot, there was just gravel and earth. The once wood-paneled walls had been stripped down to the brick and, in some places, exposed to the elements as a cold wind blew through.