Columbaria
Used since ancient times, particularly in southern Europe, this form of burial only began to establish itself in Germany with the introduction of cremation at the end of the 19th century.
What is special about this type of burial is that the actual resting place is above ground. It is a kind of burial chamber system in the form of walls or individual columns, also known as steles.
Columbaria in Mainz are made of concrete or stainless steel. This is another reason why they require little to no maintenance.