Ogham is the oldest known form of written Irish. It consists of an alphabet made of 20 characters named after types of tree and is at least years old. Inscriptions in Ogham – pronounced o-am – are thought to date back to at least the century AD.
A key to the anchient Irish Ogham alphabet—on the sides of stones, the main "stem" is vertically oriented instead of horizontal. (Image: Chambers's Twentieth Century Dictionary of the English Language/Public Domain)
Mysterious stone monument found in Kazakhstan is way bigger than Stonehenge
Serpent Stone in Aberlemno, Angus, Scotland ~ an unshaped standing stone, bearing incised Pictish symbols whose meanings are unknown. It's considered one of the finest & best-preserved Pictish symbol stones still standing in or near its original position.