[Article, Ministry of Climate and Environment, 03.08.2011]
They are among the oldest living creations in Norway, and literally have roots that go back to the Middle Ages and to the Viking Age. As biological fortresses, they preserve values that cannot be measured in monetary terms. As many as 1,500 species may be living in our rare and ancient veteran oak trees.
This is how one of the stories from the Norwegian nature starts, the story about hollow oaks. You can read this and the following stories on the attached information sheets.