NOTE THIS ARTICLE IN JERUSALEM POST 3 March 2012: Nat’l-religious group, rabbis promote layered burial
(Photos: Prague Cemetery; Brady Street Cemetery, London)
The Cemetery is in the Jewish Quarter of Prague is an example of sustainable burial. According to halakah, Jews must not destroy Jewish graves and in particular are not allowed to remove the tombstone. This meant that when the cemetery ran out of space and purchasing extra land was impossible, more layers of soil were placed on the existing graves, the old tombstones taken out and placed upon the new layer of soil. This explains why the tombstones in the cemetery are placed so closely to each other. This resulted in the cemetery having 12 layers of graves.
It was in use from the early 15th century. The numbers of grave stones and numbers of people buried there are uncertain. However, it has been estimated that there are approximately 12,000 tombstones presently visible, and there may be as many as 100,000 burials in all. It is not clear when exactly the cemetery was founded. This has been the subject of discussion of many scholars. Some claim that the cemetery is over 1000 years older than the accepted date, which is the first half of the 15th century.More details this link.