This was a huge highlight of the trip for me, it’s the ruins of Alvastra Abbey. This was a Cistercian monastery founded in 1143 by French monks from Clairvaux at the request of King Sverker I of Sweden. As the first Cistercian foundation in the country, it served as a significant religious and political hub for centuries until it was dissolved during the Protestant Reformation.
A plan of the monastery.
There may now be a few posts about the ruins here, I found the entire site fascinating and intriguing.