Some 28 Jewish gravestones dating from the 17th century were discovered in the foundation of a wall built to protect a castle in Austria.

They were discovered during restoration work earlier this year on the Ebenfurth Castle in the state of Lower Austria, according to Jewish Heritage Europe.

The gravestones, and fragments discovered with them, are dated between 1622 and 1669, Johannes Reiss, the director of the Austrian Jewish Museum in Eisenstadt, said in a post on the museum’s blog. He called it a “sensational find.”

The gravestones will be restored and displayed at the castle, according to the report.

The wall in which the gravestones were discovered was built to protect the castle from the Ottoman invasion in 1683.

Jews were up to 30% of the population of Ebenfurth by 1671, when the Jewish community was expelled.