Archaeologists in the United Kingdom have discovered a prehistoric artificial island submerged in Loch Bhorgastail, Scotland, that may be more than 5,000 years old and as ancient as Stonehenge.

[u/No_Nefariousness8879]

https://insoniaoculta.com.br/en/2026/05/crannog-scotland-ancient-structure.html

[u/Print-Over]

They are called Crannog's.

https://en.wikipedia.org/wiki/Crannog

[u/Cute_Web7648]

Why is this a “mystery of the world”? Seems like they are not uncommon and well understood.