Making a rope is not an easy task. To make a rope the way Vikings did about a thousand years ago is even harder.
First, you need to find the right one tree. Then you should remove the bark of the tree, at the right time. Then you should drop the bark on sea for three to four months before you can start turning it into rope.
After all that soaking in the water, the bark can be separated into layers and has become much more malleable.
The Norwegian creator of below video With Ensby says:
Rope maker Sarah Sjøgreen makes a traditional three-strand haul rope. Bark is naturally waterproof, and rots much more slowly compared to other materials used for construction of ropes.
This explains why an intact rope has been found in Viking things dating back to 800 AD.
Watch the video