Sedna
An embroidery technique, traditionally practised by the women of Zmijanje villages, to create geometrical patterns using blue threads.
In 2014 it was added by UNESCO in Representative List of Intangible Cultural Heritage.
There's even an actual stamp for it.
For detailed information -
  1. https://ich.unesco.org/en/RL/zmijanje-embroidery-00990
  2. http://zmijanje.com/eng/ovezu.html
  3. https://colnect.com/en/stamps/stamp/666080-Embroidery-Cultural_heritage-_Embroidery_from_Zmijanje-Bosnia_and_Herzegovina_Serbian_Admin