Among the caves, mainly because of their genetics, tree-mould caves are extraordinary. Although in Hungary, only a few was identified near Nógrádszakál, there are many more around the world.
In Japan, at the area of Fuji Volcano approximately 250 such phenomena were discovered. Most famous is the Yoshida Tainai, which is a protected natural treasure, and formed in 937 during an eruption according to the record.
In Romania Károly Móréh was first to discover and describe the tree-mould caves in Maros valley, which are located between Göde and Ratosnya villages. Their number is above 100, but only some of them are large enough to be called a cave. Their genesis can be related to the activity of Calimani–Gurghiu Volcano 5.3 million years ago.
Four large tree-mould caves are registered in the volcanic area of South and Middle Slovakia. They have been investigated thoroughly by Ludovít Gaál since 1993. Their age can be estimated as Badenian and Sarmatian Stage of the Miocene Epoch (16.3–11.6 mya), which is similar to the caves of Nógrádszakál.