I don't want to become inhuman right away. Besides, the area could also be filled. Why is what he did forbidden? Maybe it is somehow approved, but I can't imagine that.
Retaining walls up to a height of 2 m are exempt from approval. But not in setback areas.
He upgraded his property by not building the retaining wall outside the setback area. That’s where it should have gone. Ergo, he has 30m2 more usable land. Your property was damaged by this construction measure retaining wall at the border (neighbor’s view directly onto your plate), its value decreases.
Just ask the seller of the property. Or demand insight into the neighbor’s building documents out of justified interest. If he does not let you inspect them, then you know where you stand. Then just go to the building authority.
You can make a demand that he has to dismantle it. Then you can agree as a nice neighbor with him that you accept a one-time payment of 10k or a monthly payment of 50 euros. ;)
But first talk to a lawyer to see if it is worth disputing the matter.
70 cm, okay. And if I don’t want to berm it?
I’m coming back to the finished floor height again. 20 cm higher is very helpful for leveling the terrain.
Underneath the existing retaining wall, underpinning is extremely expensive. These additional costs would have to be borne by the neighbor since he filled in.
This is, in my opinion, the legal situation but no legal advice. I would be extremely annoyed if the neighbor had built here on his own authority. At least I would want to know whether the neighbor had the right to put the wall on the border here.
Sure, you probably bought as seen, so it doesn’t bother you. Only you now incur additional costs or your property has lost value.
2 m on the large property is not very much. The neighbor has at least compensated 1 m on his property.
If you do nothing, it will spread and the other neighbors will follow. ;)
Have a nice Sunday.