Chi. Chikyuu no Undou ni Tsuite

both are historical dramas taking place in Europe during the Middle Ages and dealing with religion, belief systems, and challenging the status quo of what is expected, or accepted, in their respective settings. both series are incredibly moving, thought-provoking, and heartfelt. 

One event changes the course of the entire story & characters (not for the better at first); Both historical seinens with well-written side & main characters (of course with additions for the benefit of story); The pace of the story is similar; There are both philosophical breaks and dynamic scenes (Each of the battles is well thought out and makes sense for the characters for their growth); Even if the topic of this anime is not close to you, it still captivates you with something else; 

- Both depict the harsh realities of living in a historical European setting with minimal censorship (Orb being set in 15th century Poland and Vinland Saga being set in ~10th Century North-west Europe). - Both show heavy Church/religious involvement within their respective societies and how these beliefs influence people to act as they do. - Both have a very similar vibe in terms of art style and colour palette. Both feel somewhat dark, grounded and heavy. - Both feature main characters who desire more from the world than what they can currently acceptably obtain and showcases the lengths they are willing to go for this. 

Vineland Saga and Orb take place in medieval times and are down-to-earth, with a more mature story than most anime. 

These stories take place in medieval Europe. But that's only half the similarity. On the other hand, both stories tell about the clash of different philosophies in a cruel and unpredictable world. If you want to take a look at how humanity moved towards modern ideas about the world, about morality and about the value of life, then these anime are created for you. 

If you enjoy historical fantasies that are less action-packed and more human drama-driven, like “Vineland Saga Season 2,” you will probably enjoy “Orb: On the Movements of the Earth". 

Both are very spiritual in nature. Both involve ample debates about the meaning of life. Both have a strange way of making feel full, yet empty at the same time. Both have complex characters that come and go, warming your heart as you see their lives passing and breaking your heart with every nasty thing that happens to them. Life is a mere moment, and you enjoy it while it lasts, and that's what both of these anime are trying to show us.