'Klouster' is Luxembourgish for convent: the sisters of Heisdorf Castle.
Since 1916 Heisdorf Castle, built in 1888, has belonged to the Sisters of the Christian Doctrine. Founded in Lorraine in 1718, the order came to Luxembourg in 1841; here its members are known as ‘School Sisters’. In 1919 they laid out a cemetery at the end of the park, where over 700 sisters are buried, and in 1924 they added a chapel.