Yesterday was All Souls, the day on which Catholics honour the deceaseds. Thus Grand Duke Henri visited the Cathédrale Notre-Dame to attend a mass and the benediction of the tombs. Unfortunately for us, he went on his own as we've seen larger royal turnouts on this day before.
The crypt of the Cathédrale is the last resting-place of the remains of John the Blind, Count of Luxembourg and King of Bohemia who died in 1346, all Luxembourgish Grand Dukes since the independence from the Netherlands in 1890, as well as many other members of the Grand Ducal Family. The last person who was intered at the crypt of Luxembourg's biggest church was the Grand Duke's mother Grand Duchess Joséphine-Charlotte.
Another picture is available on the homepage of the cour grand-ducale.