Unknown Grave at Roskilde Cathedral

Roskilde Cathedral is the burial ground for many of the Danish kings and queens.

However, not all burials took place inside the church and some graves can be seen outside the church walls. The most notable of the burials outside the church is Frederik IX and his wife Queen Ingrid of Sweden.

However, there are also four unknown graves beside the church that are unreadable, but are most likely priests of the church. Behind the church near the Arch of Absalon is the location of five other graves, which I covered here:
http://virtualglobetrotting.com/map/small-cemetery-behind-roskilde-cathedral-1/

Here are three more graves located near the visitor entrance of the chuch:
http://virtualglobetrotting.com/map/unknown-graves-beside-roskilde-cathedral/

Located next to the main entrance of the cathedral under the left tower, lies this blue/greenish grave of an unknown person. The grave stone is clearly visible, but is unreadable. Not much is known about this grave and I could find nothing on the internet.