An excursion down a forgotten staircase in a 12th century French church resulted not only in a lost burial vault, but in a trip back in time to the sixth century.

The discovery was part of a restoration project at the Church of Saint Philibert in Dijon, France, which was necessary because of an ill-advised decision made in the 1970s. The installation of a heated concrete slab trapped the salt-filled ground under it—the 800-year-old church was used for salt storage in the 18th and 19th centuries—and when heated, the salt caused cracking and damage to the stone church’s foundation.